Some of these got popped off and into the "key soup" for cleaning initially and I took a board apart last night and popped a set to clean it thoroughly (after I took a pic so I'd know how to return the stems to their proper places), however, there were 3 colors of stems- off-white, more off-white/lt grey and grey.
If I were to clean and use unusually marked keys for 2 boards for my trade (if it still stands) and the more plain? (would that be best?) keys for 2 boards for myself and had 6 boards left over - What are the chances I could maybe sell the boards (and for abt how much?) -
1) in bulk as-is? (dirty, some popped stems, and popped keycap soup) or
2) bulk and clean but with stems in randomly and the remaining popped "keycap soup"? Or
3) clean with random stems and remaining, non-original keycaps attached? (I don't think I have enough posts to list them for sale here )
I'm at a loss....Some of them need major cleaning - they appear to have been double stick taped to desks?
If you have the right mix of stems (you won't - there will be too many dark and not enough light) you can make the installed stems look like the ANSI set with light for letters and numbers and dark for modifiers. A lot of work for nothing unless you enjoy it, or plan to use the boards without caps. 80%-90% of your keycaps will be right, anyway, so it it just around the edges where the weirdness creeps in.
Naptha (old-fashioned cigarette light fluid in the yellow and blue plastic bottle) is the best for removing adhesive residue, but it can damage some plastics. Test first, my experience that M plastic will stand up to it, briefly, at least. Apply, wait a few seconds, wipe with paper towel, repeat. Save the fingernail for the worst parts.
The only time I have bought M terminal boards was when they were very cheap and I wanted to harvest parts. They work perfectly well (except no LEDs) since I have an outboard Teensy I can just plug in.
Somebody recently posted a $5 breakout board that appeared to do what a Teensy does at $15 less. If you installed those, you could probably sell fully working USB Model Ms and get $25-35 + shipping, even missing some keycaps.
As-is, you would be lucky to get over $15-20. Just my opinion.