That's a very nice old beast! That was very nice of the prior caretaker of the rifle to pass it on to you..

But what was the promise??

Just for a FYI Nigel Brown inn Vol. 2 British Gunmakers. page 351 does not list that address. It only shows 1991 forward, and it appears they are still in business at
Ore Trading Estate, Framlingham, Woodbridge. So the records may be available on this beauty.

Pictures of the proofs may help to narrow down the age.