Looking at the pictures it is hard to believe that this was ever a 20 bore rifle or otherwise.
I wonder if the Purdey records (which would have been a handwritten ledger) were misread. “.320” perhaps.
Externally it looks to have been built as a Rook Rifle or a light Express (.360 2 1/4” or .380 Express perhaps).
The non-alignment of the firing pins is very puzzling. Clearly they did meet the primers in the original chambering to get through Proof.
I can only assume that when the chambering cutters were set up for .410 the machinist got something badly wrong?
