It will not be the oldest by a long shot, but the oldest razor I own is a Marshes & Shepherd Ponds Works with a Queen Warrant Mark. The Ponds Works make it to be between 1840-1850.
I have one too, but it's in need of some resto. It has a fair amount of even hone wear, but is otherwise in pretty good condition given it's age.
There was a period when razor makers stamped razor's tangs with the current monarch's initial, followed by an 'R' for Royal. VR, then, denotes that a razor was made during Victoria's reign, WR during William IV's reign and GR during George IV's reign. So I date my Greaves, which is stamped 'GR,' to have been made between 1820 and 1830. At least 179 years old and one of my best shavers.
I'm so glad I saw this thread. I never knew about these stamps.
Well, that just points out something I didn't know and also about an inconsistency in uniclectica (not unheard of, I hear).
My Marshes has a WR stamp, so not queen but rather king William IV's mark, who died in 1837. Uniclectica claims Ponds Works started in 1840, that's incorrect since mine has the Ponds Works stamping on it (Marshes & Shephard itself started in 1825).
So my razor is at least 172 years old
Were these stamps simply to provide homage to the current monarch, or are they a sign of a royal warrant? It is my understanding that a warrant can continue past the death of the one that awarded it. I've seen it happen on older bowls of Yardley shaving soap, but we're talking about something a bit older here.