I've heard a lot of good things about the TS-850, and got to use one at
Field Day the last few years. So I'm thinking about buying one, but
want to avoid any "duds" if they are identifiable.

I've noticed a few ads telling about selling the 850 for parts because
they bought one used "as is" that didn't really work as advertised.
There have been references to serial numbers, like the 60K mark due to
a modification capability, but I'm not too concerned about that
particular mod. Your thoughts?