Today's Modern = Tomorrow's Classics?

If we go with the allegorical depictions as a guide, then ALL of the bullion coins issued since 1986 are classics, except the monstrously huge 5 oz ATB pucks... It used to be that the modern period started in 1934, when roll collecting started to take off, despite the Great Depression. Many dealers would stock and price singles back to '34 as a rule back in the 80s & 90s. Anything before that was considered a classic and priced individually.

This division of circulation coinage into "classic" and "modern" is a purely American phenomenon, caused by the relative stability of the US dollar.

America, Canada and Switzerland are the only three countries where such a concept can even theoretically apply, because these are the only countries in which coins designed before WWII are still being used in circulation. Everywhere else has had war, inflation or some other cause of currency reform that causes a natural division between "old" and "new" coins.

Here in Australia, for instance, we don't have "classics" and "moderns" - we have "predecimals" and "decimals", with 1966 the sharp cutoff date, when the Australian pound was replaced by the Australian dollar.

I suspect the current American divisions of "classic" and "modern" will remain unchanged, until the US dollar is replaced by something else, at which time all of the dollar-series coins will probably be re-labelled "classic".

schools in the US teach history mostly in dates, but we tend to gloss over why/how and the results after.

I would label the Shield Cents, Statehood/Territorial/DC/AtB Quarters, Post-Westward Journey Nickels, and Presidential/Sacagawea/Native American Dollars as "Ultra-modern" coins.