Kensal I think that is a case of rough drughtsmanship. All the marks on the left make sense and are Birmingham Company Proof marks for a 12 bore shotgun with 2 2/4" chambers as applied betwen 1925 and 1954. The mark that looks like a roadkill buzzard the crown and the mirror image E and the 75 are not somehting that I recognise. Sorry about the squashed buzzard bit but it was the best description I could think of. Lagopus.....