I recently looked at a 12 gauge sidelock with a London address on the barrels and Birmingham proof marks. Upon closer inspection there appears to be very faint London proofmarks also on the barrel flats. If a gun was reproofed for some reason were the old marks removed?

Thanks,

Ed

Could be one of several reasons , cosmetic so it only shows one set of marks or , the barrels may have been to hard on the action flats and was so relived by filing off the barrel flats .Has the lump [if its a dovetail ] been re-brazed ?
No real need to remove old marks but some folk do and other s don't.

Gunman, I'm looking at a picture rather than having the gun in-hand. I should have been more clear. The flats are clean as opposed to having any blue there. Could be a reblue of the barrels.

Barrel flats on Brit guns usually aren't blued.