Maltby No4 MkI Markings?

Hello all, I've had this 1941 Maltby No4 MkI 2 groove barrel going on 30 years now. It has been more of a safe queen than anything else. I take it out every 5 years or so for a little target practice. The last time I took it out I realized the wood hasn't been oiled in about 20 or so years so I went about doing it. When it was apart and oiled I saw several markings I never noticed before. I was wondering if you guys would know what some of the markings mean. I know some of them are the individual makers of the parts but I wonder more about the various stampings in the wood and the F. MacD. stampings on the metal. I'm also curious as to why there is yellow paint on the metal below the wood.

On the butt there is FR 1-43 stamped so I assume that it had a factory repair in January 1943. Beyond that I'm lost. What challenges me the most is a stenciled capital A on the butt that looks like something was there to prevent finish touching it. The photos don't show it but there is a finish build up around it. Thanks in advance for any help. - Bill

ETA: I also do know what the Broad Arrow stamp means the rest have me at a loss.

HM Co is H Morris & Co of Glasgow, CEW is C E Welsted of Croydon, subcontractors for these parts.
The paint may be just khaki that has yellowed over the years.
BLR is usually Beyond Local Repair.
F. MacD. is probably the importer.

I've found rifles that served in the Far East often have the metal hidden by wood painted to prevent rust.