We collected old cameras during the 80s. A nice tip when bargaining for one on a fleamarket is to try the shutter: there's a good chance it either won't work or will open & close very slowly, because the lube will have thickened. With persistence it'll probably loosen up again, but if the seller isn't savvy about it you can get the beast for a much lower price than they're asking.
Of course, it might not loosen up so you might just have bought a nice paperweight, but at least it'll be a cheaper paperweight than it would have been otherwise.
I got a Canon T90 on that basis for next to bugger all, think I paid £45 for it;
I took the chance on it being the standard problem of the shutter clogging up and being releaseable by changing batteries...
and then the seller contacted me asking if I wanted the 70-210mm and various other Canon FD bits they were selling too.
Thankfully being by e-mail they never got to see my instant response to that offer...
Total Bargain.
My Isolette III has the Prontor-SVS shutter and Apotar 1:4.5/85 lens, that was another Ebay bargain... Was wrongly listed as a II and only the Prontor shutter, evidently not enough people check the pictures.
Unfortuantely they, the XAs and the Box Camera I like using are too clumsy to carry on the bike so aren't getting much use just now.