Final report

Material 
Steam Corrosion (Total 
Color Vector Change) 
Wear Test (% Weight 
Change) 
139 
hours 
309 hours 
Cupronickel-Clad C110 (Incumbent 
Material) 
8.5 
–0.17 
–0.32 
Multi-Ply-Plated Steel 
2.4 
–0.07 
–0.70 
669z-Clad C110 
4.8 
–0.27 
–0.61 
2.4.5  Phase 4 Coin-Pr ocessing Equipment Testing – Round One 
Lots consisting of 40 nonsense pieces from each alternative material candidate striking trial were 
drop tested
55 
in a SCAN COIN SC4000 coin sorting machine.  These drop tests evaluated several 
55 
Although no known industry standard terminology exists for such tests, the basic elements of a “drop test” involves 
passing test pieces through a coin-processing device while measuring and recording each characteristic and property 
used by the device to validate coins in fielded units.  Comparison of these measured values to known values for 
68  

parameters critical to many types of coin-processing equipment for each nonsense piece.  These 
tests are described in detail in the Outreach Chapter. 
None of the one-cent alternative material candidates matched the EMS of incumbent one-cent 
coins.  The aluminized steel nonsense pieces were the only alternative candidate failing to meet 
the diameter size criterion, reflecting resistance to fill during striking. 
Alternative material candidates for the 5-cent coin fell into three categories. 
x  Multi-Ply-plated steel, Dura-White-plated zinc and 302HQ stainless steel nonsense pieces 
did not match the EMS of the incumbent 5-cent coin; however, these pieces did provide a 
unique EMS compared to other coins in the world. 
x  Nonsense pieces of the copper-alloy alternative material candidates, 669z, G6 mod and 
nickel-plated 31157, demonstrated a good match to the EMS of the incumbent 5-cent coin. 
x  Grade 430 stainless steel nonsense pieces were rejected by the SC4000 coin sorter as 
being ferromagnetic and were not passed through the mechanism with the preset test limits 
used during testing. 
Quarter dollar coin alternative material candidates followed the same pattern as 5-cent coin 
alternative material candidates.  The Multi-Ply-plated steel nonsense pieces had measurable EMS 
properties, but the EMS values were very different than those of the incumbent coins.  The 669z­
clad copper nonsense pieces had essentially identical measured values compared to those of the 
incumbent quarter dollar coins. 
2.4.6  Mater ial Down Select for  Round Two Str iking Tr ials 
Materials testing and Round One striking trials were intended to provide guidance for down 
selecting a more limited number of materials for Round Two striking trials.  Those materials with 
unacceptable Round One test results were dropped from Round Two striking trials, where a larger 
number of nonsense pieces were to be produced, particularly for more extensive coin-processing 
equipment testing. 
Based on poor coinability, steam corrosion and wear performance, aluminized steel was not 
considered a worthwhile candidate for further testing.  The high striking force required for 430 
stainless steel and the substantial difficulty that a purely ferromagnetic material would pose to 
coin-processing equipment caused its removal from further consideration.  One of the two trial 
Multi-Ply-plated steel alternative material candidates for the 5-cent coin was selected for further 
testing; there was no indication that the small difference in thickness of individual plated layers 
that characterized the two Round One candidates would have a substantial impact on acceptability 
of this material.  All other candidate materials were carried into Round Two striking trials 
unchanged with two minor modifications; new 5052-H32 aluminum strip was obtained from a 
source with better known material pedigree and 31157 material to be tested in the second round 
was supplied without nickel plating.  Although plating would provide a pure white surface, the 
plating step increased the costs, and it was decided that testing without plating would provide 
useful information to guide potential material selection. 
circulating coins, is useful in determining how close the measured characteristics and properties of nonsense pieces 
are to the desired values.  The measured values can also be compared to similar values of known coins and common 
slugs throughout the world to determine the likelihood of fraud or misvalidation (i.e., acceptance as a different coin 
than that intended). 
69  

Several other changes occurred in the down-selection list before Round Two striking trials began.  
After discussions with the Royal Mint (RM), it was decided that their extensive experience with 
plated-steel coinage would be useful to provide additional candidate materials in the present 
study; in addition, further assessments of plated-steel coins led to a more comprehensive 
understanding of the issues associated with a material that many are convinced is a low-cost 
option to incumbent materials used in US circulating coins.  Furthermore, the number of global 
circulating coins that are steel-based is expanding.  Accordingly, RTS planchets were procured in 
three sizes, subjected to the incoming material tests described above, and submitted for Round 
Two striking trials.  Copper-plated steel (CPS) one-cent planchets were tested, along with 5-cent 
and quarter dollar nickel-plated (aRMour™
56
) steel planchets.  The RM’s practice of maintaining 
coin weight, rather than coin thickness, resulted in some deviation from United States Mint 
specifications for planchets.  The one-cent CPS alternative material candidate was thinner than the 
incumbent one-cent coin.  The 5-cent and quarter dollar nickel-plated steel planchets were thicker 
than those for the incumbent coins.  Therefore, it is unclear whether any deviations in the 
nonsense pieces from the RM-supplied planchets are due to the material properties or to the 
deviation in planchet thickness. 
Although 302HQ stainless steel was primarily considered a viable candidate for the 5-cent coin, 
302HQ stainless steel planchets were struck in various denominations as part of a work hardening 
study for this alternative material candidate.  This alloy was originally designed to have 
exceptional ductility for fastener applications such as rivets.  An unintended consequence of this 
alloy’s high ductility is that cupping occurs during blanking—i.e., the blanks are not sufficiently 
flat to upset and strike.  CTC endeavored to work harden the 302HQ to promote cleaner blanking.  
Unfortunately, all of the available 302HQ had already been rolled to 5-cent coin gage.  CTC 
worked with Carpenter Technology to cold roll some 302HQ to quarter dollar, one-cent and dime 
coin gages, which would have increasing amounts of cold work.  Blanking was observed to be 
cleaner with reduced cupping with 302HQ in the cold-worked condition.  There was also concern 
that work hardening during striking might lead to the development of a ferromagnetic 
microstructure in this alloy.  By striking materials with different thicknesses, different degrees of 
work hardening would be induced so that a wider range of potential striking conditions could be 
investigated. 
Several quarter dollar coin-sized Dura-White-plated zinc planchets were tested in Round Two.  
The thickness of the Dura-White plating varied; planchets of plating thickness 5, 8 and 10 
microns were prepared and tested.  This effort was primarily intended to evaluate wear response 
of materials with different starting plating thickness.  Given some disappointing results with early 
wear tests under specific test conditions, further investigation was deemed necessary.  Dura­
White-plated zinc planchets were also supplied in 5-cent coin size; however, only one plating 
thickness was delivered for these planchets. 
2.4.7  Round Two Str iking Tr ials 
Round Two striking trials were conducted in similar fashion to the Round One striking trials; 
similar nonsense dies and progressive striking load trials were used to determine the minimum 
striking load necessary to produce nonsense pieces with acceptable dimensions and coin fill.  One 
thousand blanks/planchets of each alternative material candidate were prepared/acquired for use 
56 
aRMour™ is a registered trademark of the Royal Mint. 
70  

in Round Two striking trials.  Once a proper striking load was determined for a given candidate 
material-denomination combination, a striking trial run of at least 400 nonsense pieces was 
conducted at normal press production speeds.  Each striking trial was split into four 100-nonsense 
piece lots to be distributed for testing at CTC and three coin-processing equipment manufacturers 
for post-striking tests.  Any additional coins and materials were retained at the United States Mint 
in Philadelphia. 
Tables 2-28 through 2-30 show the striking loads used to produce each lot of nonsense pieces 
used for Phase 4 testing.  During Round Two striking trials, incumbent coin materials were also 
struck for each denomination tested.  These nonsense pieces were used as a baseline to determine 
if any differences in behavior of the nonsense pieces were due to the change in materials or to 
changes to the images used on the nonsense pieces.  The response of these nonsense pieces (i.e., 
those made with incumbent materials) was also compared to newly minted 2012 circulating coins 
of the same denomination. 
Table 2-28. 
Progressive Strike Results for One-Cent Coin Alternative Material Candidates – 
Round Two 
Material 
Test Coin 
Striking Load 
(tonne) 
Difference from 
Incumbent Coin 
(tonne) 
Comment 
Copper-Plated Zinc (Incumbent 
Material) 
40 
-­
N/A 
302HQ Stainless Steel 
60 
+20 
Insufficient coin fill 
Al-Mg Alloy 5052-H32 
25 
–15 
None 
Copper-Plated Steel – RM 
50 
+10 
None 
Copper-Plated Steel – JZP 
40 
0 
None 
71  

Table 2-29. 
Progressive Strike Results for 5-Cent Coin Alternative Material Candidates –  
Round Two  
Material 
Test Coin 
Striking Load 
(tonne) 
Difference from 
Incumbent Coin 
(tonne) 
Comment 
Cupronickel (Incumbent Material) 
54 
-­
N/A 
302HQ Stainless Steel 
70 
+16 
Insufficient coin fill 
G6 Mod 
54 
0 
None 
669z 
54 
0 
None 
Unplated 31157 
54 
0 
None 
Dura-White-Plated Zinc 
54 
0 
None 
Multi-Ply-Plated Steel 
60 
+6 
None 
Nickel-Plated Steel 
54 
0 
None 
Table 2-30. 
Progressive Strike Results for Quarter Dollar Coin Alternative Material Candidates 
– Round Two 
Material 
Test Coin 
Striking Load 
(tonne) 
Difference from 
Incumbent Coin 
(tonne) 
Comment 
Cupronickel-Clad C110
(Incumbent Material) 
62 
N/A 
N/A 
302HQ Stainless Steel 
73 
+11 
Poor edge fill 
Multi-Ply-Plated Steel 
65 
+3 
None 
Dura-White-Plated Zinc 
54 
–8 
None 
669z-Clad Copper 
62 
0 
None 
Nickel-Plated Steel 
65 
+3 
None 
One unexpected result of the striking trials was the lack of correlation between material Rockwell 
15T hardness and the optimum striking load used for nonsense pieces.  In several cases, such as 
Multi-Ply- and nickel-plated steel 5-cent coin alternative material candidates, two similar 
materials with substantially different hardness values did not show significant differences in 
striking performance.  A different material with a similar hardness to the nickel-plated steel 
planchet, 302HQ stainless steel, was substantially more difficult to coin.  Hardness has been a 
critical value for characterizing incoming lots of materials used by the United States Mint for 
production of incumbent coins.  Although hardness may be a good quality discriminator for 
various lots of incumbent coinage materials, in the testing completed here hardness did not 
correlate with the relative performance of different materials in the striking trials. 
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2.4.8  Obser vations of Str iking Tr ials – Round Two 
2.4.8.1  One-Cent Nonsense Pieces 
Grade 302HQ stainless steel specimens were struck to complete the blanking and ferromagnetism 
study.  No evidence of such a change was found during these trials.  Nonsense pieces were 
visually appealing at 40 tonnes as noted during progressive striking, but they were out of 
dimensional specifications.  At 50 tonnes, the nonsense pieces still did not meet dimensional 
specifications.  Dimensional specifications were met at 60 tonnes, which is 50% higher than the 
nominal 40 tonnes used for production of copper-plated zinc one-cent coins.  The remaining 
302HQ stainless steel nonsense pieces were struck at 60 tonnes.  One of the nonsense pieces 
struck at 60 tonnes is shown in Figure 2-11. 
Figure 2-11.  302HQ stainless steel one-cent nonsense piece struck at 60 tonnes. 
Aluminum alloy 5052 was obtained in the cold worked and stabilized H32 temper from a 
warehouse in the nominal one-cent coin gage.  This alloy had been a leading candidate for the 
one-cent coin because of good coinability and low cost.  During progressive striking trials, fill 
was inadequate at 20 tonnes, but nonsense pieces looked excellent when struck at 25 tonnes as 
seen in Figure 2-12.  In addition, dimensional specifications were met at a 25-tonne striking load.  
Therefore, this load was used for the subsequent striking trial. 
73  

Figure 2-12.  5052-H32 one-cent nonsense piece struck at 25 tonnes. 
Copper-plated steel planchets were obtained from the RM.  At a striking load of 35 tonnes, the 
nonsense pieces demonstrated excellent coin fill, but were inadequate in rim height.  At 40 
tonnes, the nominal striking load for the incumbent copper-plated zinc (CPZ), the nonsense pieces 
looked excellent and met the low end of dimensional specifications.  However, the planchets were 
supplied in a thinner gage than normally used by the United States Mint.
57 
Thus the rim height of 
these CPS nonsense pieces would be expected to be lower than incumbent CPZ coins.  The 
United States Mint press operator commented that the surface of these CPS nonsense pieces 
looked better than that of the incumbent CPZ one-cent coin.  At 60 tonnes of striking load, one 
United States Mint engineer remarked that the nonsense coins looked to be of numismatic 
quality.
58 
The striking trial for these CPS nonsense pieces (from RM-supplied planchets) was 
performed at 50 tonnes – see Figure 2-13 for a representative CPS nonsense piece struck at this 
load. 
57 
The Royal Mint maintained the weight of the planchet, rather than the thickness.  Since steel is approximately 10% 
more dense than zinc, the resultant CPS planchets supplied by the Royal Mint were thinner than incumbent copper-
plated zinc one-cent planchets.  
58 
Numismatic refers to high quality coins minted for collectors.  
74  

Figure 2-13.  Copper-plated steel one-cent nonsense piece struck at 50 tonnes from planchets 
supplied by the Royal Mint. 
A striking trial was performed on a second supply of CPS material.  JZP supplied CPS planchets 
having dimensions consistent with the incumbent one-cent coin.  Good results were obtained for 
nonsense pieces struck at 40 tonnes – see Figure 2-14.  One United States Mint engineer 
commented that the JZP-supplied CPS planchets struck at least as well as the incumbent CPZ 
planchets.  The rim height was on the high side of the one-cent coin dimensional specifications. 
Detailed examination under magnifying glasses showed that both of the CPS nonsense pieces had 
better coin fill than the incumbent CPZ material. 
Figure 2-14.  Copper-plated steel one-cent nonsense piece struck at 40 tonnes from planchets 
supplied by JZP. 
2.4.8.2  5-Cent Nonsense Pieces 
Stainless steel is a good candidate material for the 5-cent coin due to its expected superior wear 
and corrosion resistance, along with its expected silver-white luster.  However, coinability of the 
material, as noted in the Round One results, is an issue.  Carpenter Technology succeeded in 
75  

developing a proprietary annealing procedure to lower the hardness of 302HQ to 72.4 Rockwell 
15T.  Despite this relatively low hardness for a stainless steel, the nonsense pieces were not 
completely filled near the rim at a striking load of 70 tonnes, considerably above the nominal 54­
tonne production load for incumbent cupronickel 5-cent coins.  The maximum allowable load for 
the striking presses is 70 tonnes—a load that ensures the safety of both machinery and dies; 
therefore, the 302HQ striking trial was conducted at that load.  As seen in Figure 2-15, the 
background surfaces showed some mottling even at a 70-tonne striking load. 
Figure 2-15.  302HQ stainless steel 5-cent nonsense piece struck at 70 tonnes. 
The three copper-based alloys, G6 mod, 669z and unplated 31157, coined extremely well at the 
incumbent 5-cent coin production load of 54 tonnes.  Alloys G6 mod and 669z each had a slight 
yellow cast as seen in Figures 2-16 and 2-17, respectively.  Unplated 31157 has a golden hue to 
the naked eye as seen in Figure 2-18.  Each of these three copper alloys is a promising 5-cent coin 
alternative material candidate, since each has a very similar EMS to cupronickel. 
Figure 2-16.  G6 mod 5-cent nonsense piece struck at 54 tonnes. 
76  

Figure 2-18.  Unplated 31157 5-cent nonsense piece struck at 54 tonnes. 
Figure 2-17.  669z 5-cent nonsense piece struck at 54 tonnes. 
Dura-White-plated zinc has a zinc substrate plated with copper and then tin (Sn) is plated on the 
surface to provide a white finish.  For the 5-cent nonsense pieces, 3 microns of tin were plated. 
The Dura-White-plated zinc planchet struck extremely well (see Figure 2-19) at a striking load of 
54 tonnes.  The surface finish was grey-white. 
77  

The Multi-Ply-plated steel planchets required a higher load (66 tonnes) for complete coin fill and 
dimensional tolerance than the nominal striking load (54 tonnes) for incumbent cupronickel 
planchets.  At 60 tonnes, fill and dimensions were acceptable and the coins minted well with good 
surface detail as shown in Figure 2-20.  The additional 6 tonnes were required to ensure fill at the 
border of the coin adjacent to the rim. 
Figure 2-20.  Multi-Ply-plated steel 5-cent nonsense piece struck at 60 tonnes. 
Figure 2-19.  Dura-White-plated zinc 5-cent nonsense piece struck at 54 tonnes. 
(a)  Obverse 
(b)  Reverse 
The Royal Mint uses an electroplating process called aRMour.  The technology is used to plate 
nickel on low-carbon steel; 25 microns of nickel in the center of the coin is typically deposited for 
high-denomination coins.  A thick nickel layer is necessary for the coins to be recognized by the 
sensors in coin-processing equipment.  As discussed above, the as-received aRMour planchets 
were thicker than incumbent 5-cent planchet specifications for rim thickness.  The thicker 
78  

planchets showed good coin fill at 54 tonnes – see Figure 2-21.  Therefore, the striking trial for 
this candidate material was performed at 54 tonnes.  Due to the thicker planchets, the striking trial 
was run at a lower rate; 350 pieces/minute, to ensure proper feeding through the press. 
Figure 2-21.  Nickel-plated steel 5-cent nonsense piece struck at 54 tonnes. 
(a)  Obverse 
(b)  Reverse 
2.4.8.3  Quarter Dollar Nonsense Pieces 
As part of the cold-rolling study to improve blanking, Carpenter Technology rolled 5-cent coin 
gage to quarter dollar coin gage for stainless steel alloy 302HQ.  Blanking was performed by 
waterjet cutting because of time constraints and the cut pieces were returned to Carpenter 
Technology for a proprietary anneal.  The hardness was lowered to 73.4 Rockwell 15T as a result 
of this anneal.  Despite the low hardness, the fill during striking was poor near the rim as shown 
in Figure 2-22.  This was in spite of a 73-tonne striking load, which is above the nominal 62 
tonnes used for the incumbent quarter dollar coins.  The striking trial was performed at 73 tonnes; 
however, a United States Mint engineer cautioned that this high load might damage the machinery 
and dies during actual volume production. 
79  

(a)  Obverse 
(b)  Reverse 
Figure 2-22.  302HQ stainless steel quarter dollar nonsense piece struck at 73 tonnes. 
The Multi-Ply-plated steel nonsense pieces showed good detail at 54 tonnes, but they were not 
consistently within dimensional specification at this striking load.  Therefore, the striking trial 
was performed at 65 tonnes, but fill was inadequate at the rim and for some of the letters:  note 
that the “P” in the word “PROJECT” in Figure 2-23(a) is not completely filled.  A few nonsense 
pieces had visible plating defects.  Further research is needed to find solutions for these issues. 
Figure 2-23.  Multi-Ply-plated steel quarter dollar nonsense piece struck at 65 tonnes. 
(a)  Obverse 
(b)  Reverse 
Dura-White-plated zinc showed promise in earlier tests with the notable exception of wear 
resistance.  Planchets of three different plating thicknesses, as described in Table 2-31, applied to 
A190 zinc substrates were used in the striking trial.  Nominally, the copper layer was about 12 
microns thick and the top plating of tin varied from 5–10 microns. 
80  

Table 2-31. 
Measured Thickness* of Dura-White Plating Layers by Metallographic Sectioning