$80 is a heck of a deal either way. Did you actually verify how much RAM is in it? Keep in mind that those produced around the time of the 512k introduction would start seeing hybrid boards. Although I have only seen a few 512k hybrid boards with 128k of RAM. It would be interesting to see the sales figures for the 128k when the 512k came out. But it did apparently sell until October of '85, pretty much a year ager the 512k came out.

The floppy gum up is easy to fix luckily. I have a brand new 400k drive in box, of course it was gummed up too.