Generally, the key dates are the rarer, harder to find, the ones everyone needs, to complete their collection. The lowest final mintage number, usually, can have a big influence. So far the 1996 ASE (Bullion) with a mintage of less than 4 million is the lowest mintage number; followed by 1994, 97, 95 & 98, at under 5 million each. Today, it is not unusual for the US Mint to strike over 5 million in less than a month. Collectors are watching this year's ASE numbers, closely. But, the US Mint struck well over four million in January 2021. Watch the newly designed ASE, in the second half. Thanks for looking, @silversaver888.