It really helps to post pictures. Especially pictures of the barrels removed from the gun and the receiver flats.
Very early Controller of Proof marks did have double letters. But we do not know who they are. The fascination with Controller of Proof has always amazed me. They never touched your gun. This was a supervisory position. Some held the job for 20 or 30 years, so the marks do not help date the gun. It is like knowing who inspected your engine block, but not who made it.
Here are the Belgian proof marks
http://damascus-barrels.com/Belgian_All_Proofmarks.htmlHere are some Belgian maker marks
http://damascus-barrels.com/Belgian_Trade_Marks.htmlThe ML indicates that the gun was made by
Manufacture Liégeoise D’Armes À Feu
http://www.littlegun.be/arme%20belge/art...%20feu%20gb.htmML was a huge factory operation. They could produce a decent gun when the contract required it.
Pete