Parabola, they did not identify the maker. Since Anson and Deeley were with Westley Richards when they developed the boxlock about 20 years earlier, I wonder if the maker was Westley Richards. As far as I know, "Anson and Deeley" denotes an action type rather than a maker. The following is the reply which I received from the University of Glasgow. They also attached photos of the log book entry, which did not contain any further information about the maker of the gun.

"Thank you for your enquiry regarding the Army & Navy Shotgun, serial no. 21911. According to the Army & Navy registers of stock and sales of guns that we hold, your gun was originally purchased by Mr A.J. Hamilton on the 26th May 1898 for £8.8.0 (our ref FRAS 309/9 p 62). The date of invoice from the manufacturer is the 30th April 1898. The bore number is recorded as 20. The records state that this is an Anson and Deeley type Hammerless Shotgun."