The only likely possibility that I can find would be Leon Leclercque, a Belgian manufacturer who used a crowned "LL" as his maker's mark (see
http://www.littlegun.be/arme%20belge...0leon%20gb.htm ). The trouble is, this should also have a number of other Belgian proofs, like an "R" with a star over it, and an "ELG". Have you had the grips off (very carefully, as they will be brittle) or the cylinder completely out of the frame?