The following Q&A is excerpted from Clifford Mishler’s Coins: Questions & Answers
Q: I have a coin folder that has a hole for a 1965-D Lincoln cent, yet the coin is not listed in any catalog I have encountered. Why?
A: Coin folder and album manufacturers have in the past occasionally found the need to anticipate coin issues, drawing upon precedent, in order to maintain production and delivery schedules. Thus, when the production of your album was ordered in mid-1964, it was assumed that the Denver Mint would be minting coins bearing the traditional “D” mintmark in 1965. Such coins were never created, however, because U.S. Mint director Eva Adams in 1964 announced by decree that mintmarks would not appear on 1965-dated clad metal coins, nor the issues of future years. (Mintmarks were restored to the nation’s coinage, by the way, in 1968 in response to congressional action, at which time the placement on all denominations was moved to the obverse.)
The action taken in eliminating mintmarks was intended to alleviate a national coin shortage (which was officially attributed in large part and unjustly to coin collectors) by reducing the demand for the number of specimens of a date to be collected or set aside in rolls by speculators. Thus, the coins struck at Denver during that three-year period cannot be distinguished from those struck at Philadelphia.