I just looked it up, and yes, a whole bunch of 1964 nickels were made. It also explains why I find 1941 nickels on a fairly regular basis.
One of the reasons people always say get a redbook for some of the newest members. A quick lookup shows the mintage. And billions counts as a lot - I find more of those than I think of any other date.
Another glance at the list reveals that the 1941 mintage was not that much different from some other years in those days. I wonder why I find so many? I wonder if they were collected as souvenirs because of Pearl Harbor and were released back into circulation when the collectors died and their family realized they weren't worth much more than circulation.
Yeh, when the Gov't (and everyone else) pulled silver out of circulation in 1964 the Mint had to ramp up coin production. The production of 1964 nickels went into high speed. And if I recall correctly right into 1965 (look at the low production of 1965 dated nickels). But try and find well struck 1964 nickels. Tough to do since the Gov't was after quantity, not quality. From 1964 through about 1975 I would bet anyone that if 5 nickels were randomly drawn from circulation 3 or more would be dated 1964. And I'd win more often than not.
I find around 1 1964 in every roll, and up to 5 since I have been keeping track. I even found a 1964 with 'Ron Paul 2012' stamped on the obverse and 'end the end' on the reverse.
