So, Ed, where is there even one quotation containing an actual usage of "buck," in Canada or anywhere else, to mean "dollar" before the 1850s?

While a "buck" can denote other male mammals (such as rams and male rabbits) in context, as a general rule it means specifically a male deer. And should we believe that only the pelts of male beavers ("buck beavers" presumably) were used as currency?

Even the 1856 example of "twenty bucks" (from California) is unusual. Examples in book, periodical, and newspaper databases now available strongly suggest the word didn't become familiar nationally till the 1890s.