Here's the bike:

https://boston.craigslist.org/bmw/bik/395424334.html

Additional information:

Suntour 7 rear dérailleur
1024 steel

Unfortunately it's small for me... I'm 5'9'' and the guy said it measured ~20'' center to center.

So what is it?

I don't see how to tell for sure based on just what's there.

fwiw - I'm 5' 9", am proportioned quite "normally", and I think that bike would probably fit me quite nicely.

Yeah, i might just pick it up anyway... The guy said he was 5'7'' though, so I don't know if it'll be too small.

It turns out it's a Miyata 80-se. This is the absolute bottom of the line, right?

I decided not to get it

Assuming the wheels are alloy and true, and the bike rides decent, It may not be a bad deal for $50. Especially if the bike is rust free.

Miyata bottom of the line was still better than alot of other bikes out there.