Interesting shapes to the hammer noses... And wonderful to get additional pictures. It does look like a generic Jones-type double bite screw grip. The additional barrel lug is not a type Ive encountered before. Fixed fore-ends were more common on Continental-sourced actions (I have a Masu Brothers pinfire with a fixed fore-end, of Belgian design, but it is not a bar-in-wood), but not unknown amongst British makers. All bar-in-wood actions seem to be different from one another, and therefore all are special.

At least the (correct) serial number is in keeping with your timeline, the design and presumed date do not conflict.

There is always something to add to the story, and I look forward to the next instalments!