When I got the piano a few years ago it was horribly dirty. 24 ivories were badly chipped or missing. 3 black keys had their top missing. It had been played with the felt down (it looked like the rod fell out of the pedal bar) so the felt had perfect holes where the hammers made contact.
I’ve fixed the pedal bar. We cleaned out the innards. A friend carpenter had made me some new ebony tops. Yesterday I took a damp rag and wiped off all the dirt from the keys where the ivory had been missing. I then took a knife and scraped the new tops to make sure they’d glue well. And finally I glued down the replacement pieces. The key was to absolutely avoid water based glues. As I wait for the glue to dry I will come back with nail file and even all the new pieces out.
I am pleased that I’ll get to tickle ivories again. I know folks say plastic works fine. I disagree. I really hope they can eventually synthesize ivory. Anyway, after playing a couple tunes I really need to get around to filing down the larger keys. The slight drag causes me to miss notes.