There is only one set of British 1954-1989 proof marks, placed in 1962 at the time of the sleeving. Had the gun been built for export to England immediately after the war, there would be 1925-1954 marks, including NITRO PROOF and 1 1/8 oz.
I don't see SLEEVED on the flats or the barrels which I believe was required, on both barrels, post-1954, but could not confirm.

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