Green’s Dictionary of Slang

belvidere n.

[the statue of the Apollo Belvedere]

a good-looking man.

[UK]Barrère & Leland Dict. of Sl., Jargon and Cant.
(con. late 19C) J. Nevins ‘Western frontier gay slang’ on Twitter 2 Mar. 🌐 ‘belvidere’ = handsome butch cowboy.