<P> With the entry of the United States into World War II, nickel became a critical war material, and the Mint sought to reduce its use of the metal . On March 27, 1942, Congress authorized a nickel made of 50% copper and 50% silver, but gave the Mint the authority to vary the proportions, or add other metals, in the public interest . The Mint's greatest concern was in finding an alloy which would use no nickel, but still satisfy counterfeit detectors in vending machines . An alloy of 56% copper, 35% silver and 9% manganese proved suitable, and this alloy began to be coined into nickels from October 1942 . In the hopes of making them easy to sort out and withdraw after the war, the Mint struck all "war nickels" with a large mint mark appearing above Monticello . The mint mark P for Philadelphia was the first time that mint's mark had appeared on a US coin . The prewar composition and smaller mint mark (or no mint mark for Philadelphia) were resumed in 1946 . In a 2000 article in The Numismatist, Mark A. Benvenuto suggested that the amount of nickel saved by the switch was not significant to the war effort, but that the war nickel served as a ubiquitous reminder of the sacrifices that needed to be made for victory . </P> <P> Within the war nickel series collectors recognize two additions, one official, the other counterfeit . Some 1943 - P nickels are overdated . Here a die for the previous year was reused, allowing a "2" to be visible under the "3". In addition, a number of 1944 nickels are known without the large "P" mintmark . These were produced in 1954 by Francis LeRoy Henning, who also made counterfeit nickels with at least four other dates . </P> <P> When it became known that the Denver Mint had struck only 2,630,030 nickels in 1950, the coins (catalogued as 1950 - D) began to be widely hoarded . Speculation in them increased in the early 1960s, but prices decreased sharply in 1964 . Because they were so widely pulled from circulation, the 1950 - D is readily available today . A number of reverse dies with an S mint mark, intended for the San Francisco Mint, were created in 1955; they were not used as that mint struck no nickels that year and subsequently closed, and the unused dies were sent for use at Denver, where the S mint mark was overpunched with a D. 1949 and 1954 are other years where one mintmark was punched over another . </P> <P> Proof coins, struck at Philadelphia, had been minted for sale to collectors in 1938 and continued through 1942 . In the latter year proofs were struck in both the regular and "war nickel" compositions, after which they were discontinued . Sales of proof coins began again in 1950 and continued until 1964, when their striking was discontinued during the coin shortage . In 1966 a small change was made to the design to add the initials of the designer (FS) to the obverse, underneath Jefferson's portrait . In commemoration of that change, two proof 1966 nickels with the initials were struck and presented to him . Special mint sets, of lower quality than proof coins, were struck from 1965 to 1967 . Proof coin sales resumed in 1968, with coins struck at the reopened San Francisco facility . Coins struck at any mint between 1965 and 1967 lack mint marks . Beginning in 1968, mint marks were again used, but were moved to the lower part of the obverse, to the right of Jefferson's bust . From 1971, no nickels were struck for circulation in San Francisco--the 1971 - S was the first nickel struck in proof only since 1878 . In both 1994 and 1997 matte proof nickels, with distinctive grainy surfaces, were struck in small numbers at the Philadelphia mint for inclusion in commemorative coin sets . </P>

When was the last year they made silver nickels