For the facility’s first 15 decades, the coins made at the Philadelphia Mint did not feature a mintmark. In 1942, its sesquicentennial year, staff at the Philadelphia Mint placed a large “P” mintmark over Monticello’s dome on the reverse of the Jefferson nickel to differentiate coins made with the wartime silver composition from their copper-nickel predecessors.
In the early 1940s, as World War II raged in Europe, the Roosevelt Administration took steps to regulate the use of critical materials necessary for manufacturing arms and material. The Office of Production Management identified both copper and nickel as materials of strategic importance for manufacturing war materiel.
The War Production Board (WPB) was formalized in January 1942. Both copper and nickel were on the list of restricted strategic materials, which posed a challenge to the U.S. Mint. Recognizing this challenge, the Mint had been exploring ways to cut down on copper and nickel use since at least 1940 according to Roger Burdette’s 2012 book United States Pattern & Experimental Pieces of WWII. From late 1941 to mid-1942 the Mint produced numerous experimental five-cent pieces in different metals. Authorities even considered resurrecting the silver half dime, last produced in 1873.
On March 27, 1942, Congress approved a new alloy for the five-cent piece, 50% copper and 50% silver, but gave the Mint the authority to determine a more workable composition if necessary. After tests, an alloy composed of 56% copper, 35% silver, and 9% manganese was adopted; on September 21, 1942, the first nickels were made using the new alloy. For the San Francisco and Denver mint coins, the” S” and “D” mintmarks were enlarged and placed above Monticello’s dome. For the first time a “P” mintmark was applied to the Philadelphia Mint’s coinage, in the same place on the Jefferson nickel.
A memo from Mint Director Nellie Tayloe Ross to Treasury Secretary Henry Morgenthau dated September 1, 1942, outlines the large mintmark’s purpose: “The engraver at the Philadelphia Mint is instructed to place a Mint Mark somewhat larger than usual, directly over the dome of Monticello, on the reverse of the new coin. This, it is believed, will facilitate identification of the coins when they come in as uncurrent. However, Mr. Miller states the view that the difference in color between the new and the old coin will be sufficient to identify them readily.”
The alloy change created a distinctive subtype of Jefferson nickel frequently traded for its bullion value. Attractive Mint State examples are abundant, affording interested collectors ample opportunities to add this Philadelphia Mint “first” to their collections. Examples in grades as high as MS-67 sell for less than $100; Stack’s Bowers Galleries sold an example in a PCGS MS-67+ holder for $288 in February of 2019. The highest auction result listed on the 1942-P issue’s page on PCGS CoinFacts is $5,950, which an example in MS-68 realized on eBay on May 1, 2021.
Jefferson nickel expert Bernard Nagengast in his 2002 reference The Jefferson Nickel Analyst writes of the 1942-P issue: “[1942-P Jefferson nickels] are always very nice, without the surface roughness of the copper nickel issue. Gems are easy to find.” Examples with six “Full Steps” are “very rare,” according to Nagengast. Nagengast estimates the frequency of Five Full Step 1942-Ps at 1:10.