Oldest I have right now is a Dan Wesson .44 Magnum. One of the first ones made, according to the serial number. The frame is a nice plum color, with the cylinder and barrel/shroud is as blue/black as the day it was made.
Oldest one I've had ever was a P-38 of WWII vintage, in bad cosmetic shape, but it shot ok. My neighbor wanted it badly and when he offered me a lot more than I paid for it, I let him have it.