Nice spot Lagopus. These round-actions with Jones Rotary underlevers are rare, the action of rotating the lever with a connecting rod cocking the locks.
According to the records, Dickson only built four round-actions with Jones Rotary Lever lockup. Two were shotguns, two were double rifles. There were probably a few more but it is not reflected in sales ledger by the notation 'underlever'.
Charles Gordon ordered only two 'hammerless guns' in his buying days and one was with a Jones Rotary underlever. I have seen this gun before, in a half state of restoration, the barrels having been sleeved. Sounds like your acquaintance is finishing it off. Another one saved!