1916 DWM Artillery markings help
 

All matching except mag 1916 artillery , gents I need help with some of these markings , I've tried loading photos however I seem to be only able to load 1 will try loading more
1) trigger side plate ........... letter J inside it
2) one grip has a letter W.....(Both grips are #ed to the gun)
3)inside frame letter M
4)inside frame on top of trigger ? Letter N with two 7 and othe markings
5)reciever letter N on it plus looks like a 8 or two circles together plus a symbol to the right of the N
Any and all help and comments greatly appreciated :cheers:

RJ

More photos

Letter M

Letter N and two 7

Close up

On reciever

I think they're all workers' marks, applied as it made its way along the production line.