The Lexmark has the single-part keys, while the IBM has the double. The part number for the Lexmark is 52G9700, and the part number for the other is 52G9658.
After a very thorough cleaning (full disassembly, individual cleaning of every key, cleaning of the inside tray, cleaning of the exterior plastics, etc), they look close to new. I'll post some pics later today after I get a chance to fully test them.
I think $30 is a fair price considering the intact rivets, thorough cleaning, testing, and overall condition. They'll be shipped in a proper keyboard box with lots of padding.
Thanks for the replies guys. I'll probably put them up in the classifieds later today.