I can't tell you much, but the hammer isn't a pin fire, it's either an old fixed firing pin center fire or rimfire but my guess is center fire... They are from a revolver, but whether they came from the same revolver I don't know...
If you could, post pics of the parts separately with a ruler next to the pin side of the hammer, we might be able to get an idea of what caliber it was but I wouldn't expect much more than that unless we get really lucky