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 Replies: 20 / Views: 2,380 |
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Moderator
 United States
97685 Posts |
were 71's 40% silver? I thought that stopped in 1970.
Is that why we see some copper on the edge? A plated coin?
It was in 1975-1976 that they went to 40% silver for the Bicentennial.
EDIT: to fix a silly typo.
Edited by Dearborn
07/26/2023 3:29 pm
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Pillar of the Community
 United States
1721 Posts |
Quote:
were 71's 40% silver? I thought that stopped in 1970.
Is that why we cee some copper on the edge? No. 71's should not be silver but there are known examples made using the wrong planchet. The copper, or what appears to be copper, is intermittent. Some areas of the reed look silver. I'm hoping it's a double error. |
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Bedrock of the Community
United States
10044 Posts |
There is copper showing on the edge in some of the pictures. THis could have been plated at one time. The weight of a 40% is 11.1 to 11.9.
A clad can be 10.8 to 11.7g. So it is within tolerances of clad also.
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Pillar of the Community
United States
7174 Posts |
 closer to clad than 40%. |
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Bedrock of the Community
United States
19215 Posts |
At a glance, the coin appears to have been plated. Wonder what that feature is coming off of Kennedy's bust, pointing to the 7.
Edited by ijn1944
07/26/2023 3:27 pm
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Pillar of the Community
United States
3207 Posts |
if the copper looks red, it's not a 40%
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Moderator
United States
97685 Posts |
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Pillar of the Community
Canada
6244 Posts |
The Sigma will not show you accurate because it is not design for the test you need. This it is design for bars, bullions and not for clad or plated coins. Then the results because it is EMF is just the interpretation of the operator.
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Pillar of the Community
 United States
6561 Posts |
According to a Coin World article on an ANACS certified 40% silver 1971 Kennedy half dollar: Quote:
ANACS senior numismatist Michael Fahey said graders relied on the 40 percent silver 1971-D coin's specific gravity in making the silver-copper clad determination.
The coin's specific gravity is 9.5, close to the standard 9.53 for silver-copper clad, with a weight of 11.44 grams, within tolerance of the U.S. Mint standard 11.5-gram planchet.
Specific gravity for copper-nickel clad is 8.92 and a coin's weight is 11.34 grams. So apparently the ANACS expert grader chose not to do a direct metal test, and instead did a specific gravity test. That probably isn't too tough to accomplish, probably any high school chemistry teacher would be able to precisely measure displacement. Archimedes for the win! |
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Moderator
United States
189502 Posts |
Looking a the edge of this one, I see evidence of plating.  |
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Pillar of the Community
United States
808 Posts |
I checked weight on 13 1971 Kennedys that I have. 9 are 11.2 gms, 3 are 11.3 and one is 11.1 gms!
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Moderator
United States
97685 Posts |
I'm making ing the assumption that all 13 coins were normal copper core CuNi clad halves?
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Pillar of the Community
United States
1721 Posts |
OK. I'm going with the plated theory. Were the striations caused by the plating?
Also, I did, or think I did a correct specific gravity test. I took the dry weight and divided it by the weight suspended in water. 11.3 divided by 1.3 = 8.56 grams. Too light for a 40 percent silver coin.
Since I paid 50 cents for the coin, I'm out nothing.
Thanks for all the comments.
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Pillar of the Community
United States
6561 Posts |
There is a tutorial on this forum for a specific gravity test, for anyone else who is interested. http://goccf.com/t/39666 |
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Pillar of the Community
United States
5632 Posts |
Interesting Post, I see a 1971 Kennedy half dollar. I also see The coin shown has Very Inconsistent, Spotty Appearing "Copper Plating "... The Planchet I have seen These Kennedy's with The Striations as Seen Here. I Could see a First Year Transitional Experimental Process, For the FIRST year this 1971 KENNEDY was Minted, with the Newer Cupro-Nickel Finish.. I Believe the Coin Here is a Plating Problem, By Whom, ? Other 1971 Kennedy's Exhibit No Inconsistent Copper in the Coin, As The OP's Coin.... I Too checked a Couple rolls I have around, .............. NONE like This......  All Kennedy halves were Minted to Start in 1964, Then they were 90% Silver, No Copper Rim along the Reeds Seen.  From 1965 To and Including 1970, Kennedy halves were 40% Silver...No Copper Rim along the Reeds Seen. After 1970 They were struck for circulation in Cupro-Nickel  , Some San Francisco Strikes were 40% Silver Too, In 1975 Some Kennedy strikes were 40% Silver Too, Brown Boxes, Blue Boxes....  including and up to, 1976...... |
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Posted 07/26/2023 1:40 pm
