Right key -- Just What I Needed
It astonished me to learn I can order individual keys, especially for a laptop as old as my IBM ThinkPad X40 -- about 12 years old! Got just the right one; haven't yet installed it, but I've practiced with other keys and foresee no trouble.
One caveat: If I had noticed that the shipping option I chose (USPS first class) didn't include a tracking number, I would have upgraded to one that did. My March 13 order didn't arrive till March 30 -- it WAS almost coast-to-coast, so perhaps that was part of the reason. On account of the delay, the vendor shipped a second key, and both arrived the same day. Go figure! (And choose a shipping option that gives tracking.)