Toby
I may well be wrong but my guess is that Joes gun was originally a percussion gun and that someone has just unscrewed the breach block, which probably accommodated the nipples, then just machined a chamber into the back of the barrels. This would explain the nicely rounded back to the action which never had the nipples in them. I would think the original action formed the bases for the present action. It is non rebounding so would fit the period and my guess is that the internal hammer has just been fixed in someway to the inside of the hammer spindle. It would be nice to see how this hsa been done Joe - if ever you take the locks apart. My guess is that the pegged forend is original and the slot for the peg has been moved forward so that the barrels move back onto the face. This would not have been to big a job as the new underleaver locking lugs would have had to be fitted at the same time.
The external cocking leavers do look a bit crude, which is a shame, but they serve their purpose and have made a redundant gun a good working tool again. If you can remember the gun I would love to know if I am somewhere near the mark. Many of the Perrins guns have undergone some modifications and it is not always easy to work out what has been done to them.
John
