Concur, sell them. You'll get a minimum of $100 per, likely around $150. Especially if you clean them up nicely and test them. PS2 to USB dongles are cheap. Buy one and test all of them.
I think you should use the compressor at full power, for Science. Please report back. I wonder if it would peel the letter overlays right off the keys.
Yeah, no. One of our maint techs had an adapter come loose and got his arm sandblasted to the point of going to the hospital. With plain dust. This stuff drives a dozen major pieces of equipment and dozens of small handheld units at any given time. The handheld feeds alone are plenty overkill as is and will leave a PC spotless.
The answer, btw, for science, is that the keys come off before the lettering comes off.