Why did the mass of the us penny change?

Answer 1

Because the composition of metals in the penny has changed.

Production of the war-time cent was provided for in an Act of Congress approved on December 18, 1942, which also set as the expiration date of the authority December 31, 1946. Low-grade carbon steel formed the base of these coins, to which a zinc coating 0.005 inch (0.127 millimeter) thick was deposited on each side electrolytically as a rust preventative. Unfortunately, this coating was applied to the steel before the blanks were made leaving the rims of these coins extremely succeptible to rust. The same size was maintained, but the weight was reduced from the standard 48 grains to 42 grains (3.1 g to 2.7 g), due to the use of a lighter alloy. Production commenced on February 27, 1943, and by December 31 of that year, the three Mint facilities had produced 1,093,838,670 of the one-cent coins. The copper released for the war effort was enough to meet the combined needs of 2 cruisers, 2 destroyers, 1,243 Flying Fortresses, 120 field guns and 120 howitzers, or enough for 1,250,000 shells for large field guns. Numerous complaints about the gray color of the 1943 cents, especially that they could be mistaken for dimes, led to a change in composition. On January 1, 1944, the Mint was able to adopt a modified alloy, the supply being derived from expended shell casings which, when melted, furnished a composition similar to the original, but with a much smaller trace of tin. The original weight of 48 grains (3.1 g) was also restored. Shell casings were no longer used after 1946 and the original composition was again used. The composition of the coin was changed again in 1962. Mint officials felt that deletion of the tin content would have no adverse effect on the wearing qualities of the coin, whereas the manufacturing advantages to be gained with the alloy stabilized at 95% copper and 5% zinc would be of much benefit. Congressional authority for this modification is contained in an Act of Congress approved on September 5, 1962. During the early 1970s, the price of copper rose to a point where the cent almost contained one cent's worth of copper. This led the Mint to test alternate metals, including aluminum and bronze-clad steel. Aluminum was chosen, and in 1973, a total of 1,579,324 such coins were struck (dated 1974) and ready for public release. A few were distributed to members of the US Congress. Subsequently; aluminum was rejected because, among other reasons, it would not show up on X-rays should it be swallowed. About a dozen aluminum cents are believed to still be in the hands of collectors, although they are now considered illegal, subject to seizure by the Secret Service. One aluminum cent was donated to the Smithsonian Institution. Another is in the hands of the family of a deceased U.S. Capitol police officer, and was certified as authentic in 2005. It is known as the Toven Specimen. In mid-1982, the coin's composition changed again to copper-plated zinc. The last all-copper cents were produced by the Denver Mint on October 22, 1982. These copper-plated coins, which are still being produced today, contain 97.5% zinc and 2.5% copper, and are minted on blanks produced for the Mint by an outside manufacturer (Jarden Zinc Products). This coin is identical in size and appearance to, but at 2.5 grams is lighter than the 3.11 grams of copper cents issued before 1982, but this modification saves the Government an estimated $25 million in metal costs every year. (Both types were produced that year and all are common.) The zinc core can be readily seen if the copper plating is abraded or otherwise scraped off. It should be noted that the post-1982 cents are much more susceptible to corrosion and pitting than those made prior to 1982. Many collectors lament that even perfectly preserved post-1982 cents protected in Mint sets have begun tarnishing, developing bubbles beneath the copper coating's surface, or even corroding.

Answer 2

The mass of a US penny has changed since 1982. This is because in the year 1982 the rising price of copper forced the Mint to change the cent's composition from 95% copper and 5% zinc to 97.5% zinc and 2.5% copper.