Did you know that piano keys used to come in a set of 85 but since the late 1800s 88 keys became the norm. For some reason Bechstein persisted in putting 85 keys on their Model A piano right up into the 1920s, long after all other serious piano manufacturers had started using 88 keys as standard.
You probably all know that many antique pianos have ivory keytops made from African Elephant ivory. Obviously, this is banned now but did you know that you can still get Rhino Ivory for use as piano keytops etc.
In many ways, piano keys are the only part of the piano's action system that most players pay any attention to. The rest of the action is right there, just behind the keys, but most pianist do not concern themselves with what is inside the action chamber - this is in much the same way as I won't even dream of lifting my car bonnet if something has gone wrong. I will just leave it alone and wait for some a knowledgable mechanic to come to my rescue.
If you are in need of some photos of piano keys, I can personally recommend you visit www.markgoodwinpianos.co.uk and view some of the Bechstein grand piano pages because many of them include some good closeup shots of piano keys - some in great condition. Others in poor condition.