Mike, Lot 40 made by Hiram Walker, apparently the flavoring whisky used for the Corby label's Royal Reserve Canadian Whisky (a local blended whisky), was made with a combination of malted and unmalted barley. Thus, not 100 malted barley but closer than the current American ryes excepting Old Potrero. And in fact Lot 40 and Old Potrero bear a certain resemblance in taste. Lot 40, said to be 8 years old, probably is what Potrero would taste like if allowed to age beyond 2 or 3 years. Personally I find both products unusual in palate and in particular "feinty", i.e. a scent and taste akin to"paint thinner" or "varnish" is apparent. I realise many think this is a hallmark of 1800's rye but I wonder... John's 1930's-era Monticello rye tasted at last gazebo [John, by the way I like the new corn whiskey piece you posted recently on
http://www.ellenjay.com] didn't taste at all like that and I would think was closer to a 19th centur rye spec than a current one. Ditto Dave Dogano's great Maryland ryes from the 1950's-60's tasted at the same event. These had a toasty, rich, clean and spicy (but not congeneric) taste. They did not taste like the ryes of today (possibly because today's ryes use more corn than the Maryland ones did) or the bourbon of today. They tasted of themselves, and I believe they are closer to an 1800's pure rye taste than Potrero or Lot 40.
My conclusion: I don't think the taste of Potrero and Lot 40 is the invariable result of using all-rye. There is e.g., the question of the cut taken (particularly with Potrero and Lot 40, both pot still products). Yes, in the mid-1800's there were many pot stills being used but I think distillers knew how to shape the cut to avoid what was called an "empyreutic" taste. That word, used in Byrn's Practical Distiller written in the 1860's in Philadelphia, means an off or vegetal taste, an oily or other bad taste that distillers tried to avoid. He indicates many ways to do that, everything from multiple distillations to flavoring the whiskey to filtering it. The other 1800's whiskey writers I have read made similar recommendations. The gent that sent a 1960's (or older) Overholt to that gazebo gave us the chance again to see what a classic high rye recipe would produce in only a four year old whiskey (or maybe it was slightly older then): again no taste resemblance to Potrero or Lot 40.
Even allowing for differing and changing grains, recipes and processes, all this suggests to me Potrero and Lot 40 probably duplicated the style of some rye whiskey of the 1800's, but not necessarily the best grades. For the historical purposes of Maytag and possibly also for the Hiram Walker employee, Booth, who distilled Lot 40, the palate that resulted in their respective whiskies was an intentional replication of the feinty-like palate. But in my view this flavour was not characteristic of all pure or other rye whiskey in the 1800's and likely did not represent the best of it.
Gary