I take the ad for what it says, an ad which refers to bonded goods, to technical terms like "rye malt", and to being an "anti-trust" supplier - all indicia of frankness and honesty. And anyway, even if the goods were fake, the appeal to advanced age showed that people thought such goods were superior and worth the money - this at a time when scotch whisky had almost no sale in America, and brandy from France ditto. Why would they think that, what cult of oldness would have existed then to sustain such belief? One could as well think that something very aged would be less good, as in cheese say, or hung beef.
Still, I recall the statement (1885) from the experienced Joseph Fleischman that caution should be exercised in regard to old whiskey - but he doesn't say how old.
On page 140 of the book, a reproduced price list from 1896 advertises "Old Kentucky Bourbon, 1880" (16 years old), "Cabinet Bourbon, 1885" (11 year old), "Nectar Bourbon, 1890" (6 years old), and Magnolia Bourbon which is called "new" (presumably less than 6 years old). The new bourbon is the least costly although the price differential between all of them is not that great. However as the legend states, prices were remarkably low then, and aged whiskey obviously was available, so the spread then may have been less than it was in 1910, say. The most expensive whiskey is "Old McBrayer" - with no age statement! Why, I don't know, maybe it was not bottled with an age statement and the consumer relied on the inherent quality of the taste, whatever the age.
I just don't believe in 1886 vendors could command more money for extra-aged whiskey if they, and consumers, didn't think it was better than 6 year old bourbon.
Maybe most specialists, as presumably Fleischman, then as now, felt no whisky over 6-8 years old was in fact a superior product (although this is not clear to me either), but that well-aged bourbon and rye were available in the normal market well before Volstead seems incontestable.
Gary