Mr W martin,
The 1940 edition of Stoeger's The Shooter's Bible contains a helpful ad. The top Rigby grade was the "Regal." The second was the Sandringham" - both of which were sidelocks. Next came the the "Sackville" and then the "Chatsworth" - both of which were boxlocks. The Chatsworth was priced at 35 Guineas ($285.00). Think of it as A,B,C & D.

Kiwi - He (the vendor) was misinformed. It was a Col. E.J. O'Meara.