Hi mate... finally got a bit of serial number info. He said it is B254XX. from my interpretation of your sheets and the pics and info from the owner, it was likely assembled in 1935 and refurbed at the start of WW2... Dec 1939 to early 1940, and then had a foreend replaced in service later (still depending on a number on the foreend. Main reason is there are several other rifles within a couple of hundred either side of his in the 1935 column. The '39 dated barrel was a replacement at time of refurb and the later manufacture foreend was a replacement (probably in service) a couple of years after this.

I am still trying to find out the serial number on the foreend (Slaz made, so will be 1942 onwards) to confirm it was replaced in service. Not likely a bubba rifle rebuilt, as it still has it's matching nosecap.

Very interested on your perspective please....