Amazing!
I have been gushing about these behemoths for a year, and yesterday afternoon my motherboard died and I missed all this fun!
My fantasies about stumbling across a hoard of these has come true - for somebody else!
About my wiki about bolt-modding these beasts, I am a bit regretful that I might have made people over-zealous to do it.
If you can slide-fit them back together, that is a less-destructive-invasive procedure, and you can always do the bolt-mod later.
The foam pad replacement and epoxy case repairs may come in handy for some of you.
My experience is the same as Dorkvader's, Model M keys interchange easily except for the spacebar, assuming that you are replacing the long keys such as Shift and Enter with the later (post-1989) ones with stabilizer inserts in the barrels ("chimneys"). Otherwise, I think that all the F wire stabilizers are smaller in diameter than the M wires, a mod to accept the larger wires is on my "to-do" list, but farther down the line.
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Fortunately for my empty wallet, I have 3 beautiful specimens of the F-122, so I am not even going to think about adding to my collection, but, having scoured many sources for these, for the better part of 2 years, I can say that you should grab a nice one whenever you can find it.
I have paid anywhere from $35 to $85 for these, usually filthy and/or broken, always with missing keycaps, and been fairly diligent about it.
$50 + shipping is quite reasonable for a nice complete clean one, $85 would not be out of line at all, in my opinion.
Too bad that shipping to and from Canada is very painful.