muffet, thank you for the reply.

I'm attaching another picture showing the proof marks.
Thought I might add more information to help confirm what this may have been or where it started out.

I understand the shield with the AC over P designates an early Lithgow, is that true?

As for the rest of the parts, the stock is stamped MA Lithgow, butt plate is MA, rear sight is OA 42, slaz 41 also stamped on butt stock behind trigger guard. Magazine is OA 4, barrel band is OA and the bolt BA. So many more Australianicon parts than Britishicon.
The barrel is stamped with a crown over crossed flags with L over P which is Lithgow.
Also crown over number 1 over L which is early Lithgow SAF.
Attachment 79632
I plan to do a full disassembly and see if there are additional markings.

Anyhow, I hope this added information helps.
Thank you