Welcome to the board. What a nice question as a first post!
Briefly, it is an underlever hammer Cape gun. Army & Navy was a co-op stared by British military officers for the purpose of provisioning themselves with wine at fair prices - the business model worked and A&N quickly expanded into many lines of goods, including guns. A&N supplied Birminghm made, many by Webly & Scott, guns in all original quality grades, farmer/colonial to best work. Cape guns were generally bought as all-around hunting guns by settlers and explorers; hunters tended to buy more purpose built guns.
If you care to, the University of Glasgow holds the A&N records and will research your serial number for a modest fee.
It is easy to post ditital photos and they are very helpful in valuation.
