7.62 No4 MKI conversion question

[Brit plumber]

Parker Hale sold a quantity of No4 Mk2 actions, or perhaps whole rifles, at some point in the 60s, as several in the 1954/55 range have turned up here as genuine DCRA conversions. I've had two over the years. The marking being thus:

Parker-Hale
Birmingham

Small stamping right on the barrel ring top centre.

I see!