Ok, so I have googled and tried to search and find out how much pennies weigh and when the transitions were and what they were but I can't find anything that doesn't contradict the last thing I read from the next. The 3 pennies I have in question are 1971 (3.0) , 1972 (3.1) , 1988 (2.5) .. all the other pennies I have from my pocket today weigh 3.1 and they are from 1960 to 1980.
Those are all fine. Copper plate zinc cents should be 2.5 and copper cents should be 3.1. Granted there is a mint tolerance of ~0.1g.
Are you thinking about the 1965 transition from 90% silver to clad for dimes, quarters and halves? (Nickels haven't changed their composition since they were introduced in the 1860s, except for the 35% silver ones issued from 1942-1945.)
Tolerances --> https://www.law.cornell.edu/uscode/text/31/5113 Weights --> https://www.usmint.gov/learn/coin-and-medal-programs/coin-specifications
Weights and Tolerances for Lincoln Cents: Copper Cent = 3.110g +/- 0.130g Steel cent = 2.689g/2.754g +/- 0.130g (Heavier weight produced in late 1943) Zinc Cent = 2.500g +/- 0.100g Thickness: 1.52 mm (-0.102 mm/+0.152 mm) A brief history: The composition of the Lincoln Cent (except for 1943 when the cent was zinc coated steel and except for 1944–1946 when the composition was brass [“shell case copper”] 95% copper, 5% zinc) up to 1962 was 95% copper and 5% tin and zinc (this composition is also seen in the uncirculated version of the 2009 Lincoln Bicentennial One Cent Program). In 1962 the cent’s tin content, which was quite small, was removed. This alloy of 95% copper and 5% zinc remained until 1982 when the composition was changed to what is commonly called copper plated zinc. Cents of both compositions appeared in 1982 (some 1982 cents were actually struck in 1981). “The first zinc-based Lincoln cents were struck at the West Point Mint on January 7, 1982. These coins, along with 1,587,245 business-strike zinc cents made at the San Francisco Mint that year, do not contain mintmarks; the Philadelphia Mint would take up production of the new zinc cents early in the year as well. However, the Denver Mint did not strike the new zinc pennies until October 21 - a little more than one month after the U.S. Mint decided it was time to create a new obverse master hub that resulted in a smaller-sized date.” (Coin Week) This Zinc Alloy from 1982 is actually Zinc Alloy 190 electroplated with 8 microns of copper. (ALTERNATIVE METALS STUDY Contract Number: TM-HQ-11-C-0049 FINAL REPORT August 31, 2012 by Concurrent Technologies Corporation, Submitted to: United States Mint, Page 1, Section 1.1) ALLOY 190: COMPOSITION (% by Weight) Lead = 0.005 max; Iron = 0.010 max; Cadmium = 0.005 max; Copper = 0.7 to 0.9; Zinc = Balance. (Jarden Zinc, 8/12/2015)
Pete , I have seen the 0.100 gram tolerance mentioned before in various posts, but where is that found in the government publications? The tolerances I quoted above does not separate the zinc cent tolerance from the previous. I would appreciate the basis of the 0.100 grams. One other forum used a formula of .13X2.50/3.11=.10 ( rounded), but I can't find that in government tolerances below , which were last approved in1988 in this info. Thanks Jim Tolerances --> https://www.law.cornell.edu/uscode/text/31/5113
I hate to complicate this, but I've heard that there exists one (or more?) 1983 cents with the old composition and the 3.11 g weight. Excessively rare.
I had heard that the +/- .13 carried over to the zinc, until a mod here said there was a new tolerance for the 2.5 and it was +/- .10.
I have the Coin World Almanac from 2011 and it says tolerance on the zinc cent is 0.100 gram. The Almanac states its source as the US Mint.
Because it appears that nobody really uses the frequently asked questions forum... seemed like the best place to get some answers
I ment 65. Not 85 lol... I read somewhere that all dimes and quarters were transitioned from silver in 65.. was wondering if the transition from copper to zinc for pennies was the same time