I recently came into a Webley MkVI revolver. It has some markings I don't understand. The right side of the frame and barrel are devoid of all markings. The left side of the frame has 'Webley Mark VI patents 1919' and in general has a lot of proof/view marks that appear to be of British origin but not that I have a record of. But the biggest question is, on the left side of the frame and barrel there is a large (Approx 3/16" high) upper case 'D' with a small arrowhead inside inside the 'D' pointing up. Can anybody tell me what this marking indicates ?

Thank you for any information you can provide.

Bandorigo