'68-D half dollar "experiment".
I put "162" really nice '68-D half dollars in a safety deposit box in a humidity controlled bank in the late-'70s. Unfortunately I left them in the mint set plastic. I don't recall all the sources but most of these were cherry picked from a dealer who was cutting up a large quantity of sets and had more of the '68's than he needed.
Out of "162" coins only "4" didn't require a soak in alcohol. "111" of the coins were chBU or better after cleaning and "51" were ruined by spotting. There were "9" Gems and "2" PL's.
Usually only about 45% of '68 mint set halfs on the market clean up OK but this drops every year.
"Retail friendly" sets are getting very difficult to find since every set has at least a little discoloration on almost all coins. I'm seeing some really large premiums to market for retail sets. The '69 is toughest followed closely by the '70, and then the '68.
In the past most '68 mint sets accumulated by wholesalers ended up in sets. For many years most dealers just cut them up for the cash register. Now it appears that most accumulations are being cut up for singles to supply this burgeoning market. "Retail friendly" '68 singles sell for $7.50 for the half, $2.50 for the quarters, $1.50 for the dimes, and $1 each for the rest.
Of course as the number of sets decreases and the percentage that can be cleaned plummets it's just a matter of time before demand overtakes the supply. A lot of the few still acceptable sets will tarnish if those paying retail prices allow it.
These are interesting times for moderns. Perhaps not as exciting as a year ago but all the trends in place then are continuing. I suppose the acceleration in demand might have eased a little from an extremely high level.