Finally took possession of the Jeffery 12-bore today.
Great to know the plod are keeping the community safe by having this vintage game gun parked in my dealer's vault for 28 days. Grrr!

To answer your earlier query Clayton, the fore-end fastener is indeed the Anson push-rod:

...and I might put off trimming the stock extension for the present as it has a pattern of skip-line checkering as a butt-plate:

Screws are missing though. Must be well glued!

Regarding the loads I might be comfortable putting through this dainty gun, I will have to err on the side of caution as the lumps are tiny.
Compared to the Greener Empire, microscopic!

Of course, the screw-grip third bite will increase strength considerably.
Barrel flats show original nitro proof for 1 1/8 oz loads.

Hopefully off to the pattern plate on the weekend!

Will check barrel wall thickness before committing, but they feel correct weight.