Originally Posted By: Kutter
It wasn't required of the Proof House under any law AFAIK,,or was it?
London didn't mark any yr of proof date or code of date/proofing till the early 70's I don't think.



Neither the Birmingham date code mark nor the later London date mark was a required proofmark. But both come in handy to pin an exact date on a gun--especially if there are no makers' records to rely on.