If by give you mean you can flex them if you squeeze the front to the back, I would say they could be ivory. If they are thin like the ones looking edgeways in post 27 they are probably ivory. Collarless pins and all. If they are thick and have collars I doubt it.
Those ivory single action grips are bad to the bone. I always thought about putting a set on my SAA 44spll but the spirit is willing and the wallet is weak.