Just picked up a snotter of a Gillette Old on EBay.
Quite a lot of brassing and the usual cracks in the handle. Only bought it for trying so that doesn't matter.
However, it does have a stamp on the head with a G inside a D. Apparently (according to some blurb I read) that means it was returned to Gillette for a free repair and Gillette stamped it so it couldn't be repaired twice?
That's what I'd read but then I received a NOS Old Type that was still sealed which had that stamp on it, so now I'm not so sure. I've only ever seen it on silver plated Gillettes, so maybe it's a sort of hallmark.