That's very kind of you, but I had actually just downloaded a rip to check for that last post I made.
Anyway, Mednafen more-or-less answered our question for us. If our only options are 31.5kHz, 15.8kHz and a couple that are much less than that, we can be pretty sure that most games use 31.5kHz. 15.8kHz sounds pretty low-fi. used 16kHz streaming music, to give you an idea (although it also had an 8-bit sample rate instead of 16). The only question left is whether each video is in stereo or mono.