Frazetta had a few covers on the Christie's East auction catalogs in the way back, but I think Mothman was the only back cover. I also dunnae think these two go together, but wadda I know? I only got one catalog, and that one wasnae for the covers, but for a rare Barry Smith that I couln't find anywhere else (I believe you'd search unpublished Barry Smith on here).
Ooops! Just did the the search myself, and that was a Sotherby's catalog, so I've never had a Christie's East