Grandfather is long gone (this gun was apparently a gift to him, when he turned 19, in 1919.
Not this gun.
This gun was built and finished by Webley & Scott. Hard to say which specific model without a photo of the top of the action. Engraving is Webley's style. Army & Navy's number of 68,3XX is actually quite a late number for them, and would be in volume 10 of their records, which covers the period 1927-1935. The number 113,2XX is Webley's serial number, and is from 1929. The proof marks include the chamber length mark (2 1/2") introduced by new rules of proof in 1925. A & N's records will probably show 1929 or 1930. You can request a copy of the ledger page for this gun. Email the Archivist at the University of Glasgow. They will provide the year the gun was sold and who it was sold to free via email. If you want hard copy of the ledger, they charge 25 GBP, IIRC. Their records will include both of the numbers mentioned above, date of order, date of sale, the make profit code, name of buyer, who built the gun, etc. It's a neat thing to have, especially if the gun has been handed down in the family.
Another potential way to check the date, if your gun was proved in Birmingham (the quick check is the view mark on the flats. Birmingham's is a crown over BV, London's is a crown over V), it should bear a date code. This is a small mark on the flats consisting of a pair of crossed swords with a letter in the 12 o'clock angle and a numeral in the 6 o'clock angle. The letter is the date code. If it was proved in London, there will be no date code. Your gun was built and finished in Birmingham. That doesn't mean it was proved there. Webley had many thousands of double guns proved in London.
