The bike is prolly pre Grant Petersen (a rather idosyncratic and respected designer). I'd say 129$ is high for that thrift store bike. $50 tops for what you have described, although old bike pricing runs higher in some urban areas (NYC, for example). Slightly later, petersen designed Bstones certainly have a cult following and are worth more. I have an RB2, a mid-level Petersen Bstone, and it more than holds it's own against the expensive Italians some of my ride partners haul around (of course, this difference is entirely due to the sterling engine powering the RB2
). I do like that bike. Well worth the 40$ I paid for it.
Despite Syd's POC comment, by that period you get a bike that is very well put together and prolly would make a very good beater/utility ride. And the Cyclone mechs are real nice, IME. But at that price, I'd keep looking.
The rust on the HS likely can be cleaned off with a bit of brass wool. As long as to the races are okay, the HS is likely good. Can't tell until you look inside.