I have no way to know how many miles these IG cassettes have on them. I got the 850 for free off Craigslist; somebody around the corner from me had posted it as a "for free, needs tires" kind of listing. It was fairly dirty, but only from sitting outside. The crankset and cassette visually look okay, but I really don't know how much use they've had.

If I'm honest, I don't have climbs that I stand up for (I just go slower), and I climb the largest climbs in the smallest chain ring and on the large half of the cassette, so I could probably run these cassettes for many years. I'm not putting a lot of power through the drivetrain on a continual basis.

I think this is right -- I remember reading something like this. I do know that I could assemble a 7-speed cassette out of the 8 or 9 loose cogs that I had (with the 8-speed spacers), but shifting was never perfect. I also know that the two-letter code on all of the cogs didn't always match, meaning they weren't designed to be in the same cassette together. I understand this also has shifting implications. He gave me a bunch of stuff from his racing days with no warranties implied, and I knew it was a hodge-podge of parts, but I do like trying to get old stuff to work together. I think this particular set of cogs, though, is not gonna work. I may go back and see what I need and, if it's just one cog or two that I'm missing, I may try to find just those particular ones.

I did sell off the Dura-Ace front derailleur and the 42-53 105 crankset, but I kept the cassette cogs for a rainy day. Maybe I'll make something out of them yet.