Perhaps Himes, N.E. (1936) _Medical History of Contraception_, Allen and Wnwin, would be of assistance. Mind you, I haven't read it, only saw it cited in James, Peter and Nick Thorpe (1994) _Ancient Inventions_, Ballantine Books, NY. They agree that the earliest description of a condom was by Fallopius in 1564. They think his was "a refinement of an earlier device" (p.191) and give various theories about condoms used by Romans and earlier.