This is the second of at least 4 General Motors designs made in the late 1960s that feature a Lincoln head obverse. They were originally described as being made of 'powdered metal' but, according to Ken Potter, are actually made of bronze. This variety is not listed in Pollock. It uses the same Lincoln obverse as P4055 combined with a different reverse die. We are calling it P4056. According to Ken Potter, die varieties exist. Around a dozen are believed to exist. StacksBowers 8/22 sale describes the first of 2 examples as follows: "Although once thought to have been a product of the United States Mint, the dies from which this type was struck are attributed to General Motors. They were made without official U.S. government knowledge at the firm's Tech Center in Warren, Michigan on an electrical discharge machine (EDM). Actual Lincoln cents acted as models in the Elox EDM machine, which created the dies through the spark erosion process. A product of General Motors earlier testing as part of this project, these pieces were struck on one of the first prototype roller presses. Rare." This first example had thinner rims and is dated to August 1964 while the second with broader rims is dated to January 1965. Additional information on these pieces can be found in Pollock. Photo courtesy of Ken Potter.