Before Al Gore invented the internet, gun magazines were the standard of disseminating info for the world of shooting, guns and certainly handloading. Perhaps one of the finest gun writers that ever lived and plied his trade was Skeeter Skelton and his writing influenced more than a generation of handloaders, and Skeeter was a big lover of Hercules Unique.
I bought a load old gun magazines running from the late 1960's through the mid-1980's in one fell swoop, I think I paid ten bucks and it FILLED it little red wagon (like a Radio Flyer) at the Coon Dog Nationals in Kenton, 1991 or maybe 1992. So while I wasn't a gun magazine reader when Skeeter was actively being published, I have read a large portion of what he's written in my old issues of Shooting Times.
I'm willing to bet that if you were a handloader in the 1960's or 70's, if you owned revolvers and you were American, you had Unique and you used Unique. You may very well have used more Unique than any other powder unless you were a bullseye or PPC shooter, in which case you burned more Bullseye.