That is super cheap, but me thinks it's probably a mid 70's if it's going for that price. My '68 was around $1,200 a few years ago...I think they have gone up since then. Damn I miss that amp.
the only silverfaces i have played were the ones with master volumes, and imho, they suck donkeybawls. gawd.... terrible, sterile tone. oh, but they are "vintage" and say "fender" on them, so it automatically means they are good.
of course though, i love some fender. the best amp i've ever played is an original '59 bassman.