From 1920 to 1933, the only way to drink whiskey in America was to get a doctor's prescription, which would be pasted on the bottle (max one bottle/person/week) — much like the "medical marijuana" of today.
Adam from the LA Whiskey Society held a tasting for a dozen pints of surviving Prohibition-era whiskey (including one brand whose label was so far gone they don't know what it was). The booze was surprisingly good!
I (Adam) have a personal fascination with Prohibition-era whiskey. I'll sometimes share my collection with other bourbon connoissuers — many are bemused when they see the pints. "Hmmmm," they frown, disappointed. "I've never heard of most of these."
Well, of course you haven't! The current era of bourbon enthusiasm is based on the products of about seven US distilleries. But before Prohibition, the US had thousands of distilleries! 183 in Kentucky alone. (When the Bottled-in-Bond act took effect in 1896, the nationwide count was reportedly over eight thousand). Each distillery produced many, many different brands.
Prohibition destroyed almost all of those historic distilleries. Pints like these are all that are left of the products they once made.
A note about what are now known as "DSP" numbers — before Prohibition, every whiskey-producing state was divided up into districts, with distilleries in every district numbered starting at 1. A Pre-Pro distillery is identified by the state, the distillery number, and the district number. Years later, after Repeal, the scarcity of distilleries meant that any which still existed just kept their distillery number, and the districts were discarded.
[LA Whiskey Society]