Coupla things to watch.
Look at the valve body. If it's grey/white color, it's die cast Zinc. If it's yellow, it's brass. The zinc ones are a bit sensitive to having the threads torqued too much, and will strip out if not handled with some care. The brass valve bodies are not readily available.
Look at where the hammer hits the valve. Does it hit the valve directly, or does it strike a transfer bar. The transfer bar eats a tiny bit of the energy of the hammer strike, and can result in a less powerful gun when all is as good as it gets. The direct strike valved models can be tuned a bit higher than the transfer bar ones.
But the real point is to point out that there are a couple different variants during the production run, and to watch for the changes, as they may cause parts to not be correct, depending on what you are looking for, if anything.
The cylinder itself may be metal or plastic, IIRC. They can be adjusted to give the best timing possible (alignment of the cylinder and barrel) and this allows a little better power.
Mac1 Airguns site has a bit to say about the Crosman Revolvers.
I have a couple around. Fun to shoot, if you don't mind the cost of powerlets.
The 22 pellets will lay some pretty good smack on a pop bottle or can, too.
Cheers
Trev