When I was a kid we had a very old upright piano.
The keys were made from real ivory. Other old pianos normally had keys made from bone. The keys were in perfect condition, the rest of the piano.... not so much.
Our piano teacher hated the piano and spent years trying to convince us to buy a new one. Which we eventually did.
I sometimes wonder whether those keys would have been worth a bit of money to someone looking to restore an old piano. We gave that piano to my sister's best friend and her parents traded it in on a new piano a few years later while she was overseas.
My wife has an electric piano (nothing fancy) somewhere around the house. She refuses to get it out of storage as she really likes our upright acoustic piano and thinks I should play that instead. Except that the upright acoustic piano was kept under a leaky air conditioner for years and the keys are shot, the action is shot, the sound isn't that good, it's out of tune.
In my father's work he had many contacts, including an old guy who restored pianos and basically all mechanical key operated instruments.
When I first met him he was restoring the steam operated huge leather bellows that powered a pipe organ from the 1800s in a massive Catholic Church. All the steam parts were just fine after one hundred or so years, but the twelve foot tall leather bellows had developed holes and no longer worked properly.
From his description and my only trip with him, one had to arrive at the church five hours before services to start a boiler which simply operated a single steam piston engine in a separate building. Once the steam engine was going you could begin to operate the bellows, which fed pressure into another massive air-tight part of the remote building. All the pressure was then sent a room sized "manifold" which THEN powered the pipes of the organ.
It was one of those days when I had my camera around my neck, but I was too astounded by my surroundings to take a moment to snap pics.
Anyway, on that day this old salty fellow taught me how to tell the difference between real ivory keys, which this old pipe organ had, and the two odd keys that had been replaced with probably bovine bone in the past.
Back to the point: The real ivory keys show a circular grain structure, while the cheap replacement cowbone keys had a linear grain structure.
I can tell you if it was real ivory those keys would still be worth their weight in gold.