First time poster with a question

[Strangely Brown]

I don't remember ever seeing exactly those markings on a Mk.I/2 conversion: too deep and too neat, and no mention of where and when the work was done.

Is this perhaps a conversion done in the civilian world?

My thoughts too.

Giving it some thought and desperately trying to remember some images lost when my "new" computer went tits up I'm leaning towards AJ Parker rather than Parker-Hale.
Fultons could also be in the frame for this given that at some time they either tweaked the rifle for a customer or did the complete conversion work themselves.