Apologies if this is not the correct forum. I have a Rigby 350 rifle sold in 1910 with markings on the stock which I have been hoping to learn more about. The rifle's bore is excellent, the finish on the metal mostly gone, the stock has a dull finish but not damaged. I would say well used but well cared for. Arrived with a similarly well used leather sling with tapered ends passed through eyelets on stock and barrel and knotted.
Rigby records indicate that when sold was fitted with a "telescope", the original bases remain in place.
There is a non-factory (I presume) stamp on the stock "KAT" with a line under and below the line another "A" and below that "9020".
Google has not been enlightening as to what the stock marking might be. I guess some sort of inventory? Military mark?
Any information, best guesses, fun theories much appreciated,
Thank you.

Just a guess. KAT may relate in some way to the KAR (Kings African Rifles) regiment active in East Africa. The British army experimented with "elephant guns" as anti-armoured vehicle weapons. The author, Gavin Maxwell, who was the small-arms instructor for the SOE during WWII had a Rigby 350 which he acquired during the war.