Just bought at auction, searching for history info...........

[Beerhunter]

On the end of the muzzle, right side, it appears to be stamped, NP.3C, 3" 2.22", and under this, TC NS.

Sound like Gunmakers Company (London) Proof. It means that it has been through the British Gun Trade at some point.

BTW if you look carefully you will see that it it reads "NP .303" and thee last bit is "TONS [] inch" (square inch)

As to what it is: you have a No.4 Mk.1 that has been FTR (Factory Thorough Repair) at Fazackerly, Liverpool, England; which was later (from your description) Bubba'd.