Bill:

In those days, they didn't use a jacketed bullet for proof. IIRC, they used a lead bullet wrapped in greased paper that would have been heavier than 310 grains.

The Webley number probably isn't on the short rib, it's more likely on the left side of the fore-end loop. If it's a Rigby boxlock, it's a Webley product and the number will be there somewhere. Very, very few Rigby boxlock rifles came from other makers.
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