Novice question - P.O.F. No4 Mk1 - Manufactured from scratch or FTR'd from parts

I have (almost) a No4 Mk1 parts rifle marked No4 Mk1 53/POF/A2??? with A2??? on the wrist.
I have been told that POF did not manufacture Mk1's but that they were effectively FTR's. On the other hand, I found a thread on another forum stating that BSA sold their No4 manufacturing kit to POF around 1950.
Can anyone clarify if these rifles were "manufactured" from scratch by POF or would they have been assembled on re-manufactured actions?.
It has a greenish parkerised finish and the serial number on the wrist looks similar to my BSA actioned "bitsa" and only 200 or so away which seems to indicate it may originally have been a BSA action.

POF made No4 MkI's from 1952 until 1957 using BSA-Shirley machinery. I have been tracking POF made rifles and of the 60+ rifles I have info on to date, nine are MkI's. From the data I have collected, yours is the first 1953 "A" prefix letter four digit serial number. Prior to yours, it looked like 1953 production changed to a "B" prefix letter and five digit serial number.