During the KRA seminar on John Armstrong and his apprentices it was mentioned that Armstrong had 3 documented apprentices prior to Nathaniel Rowe (1836). I've seen one Wickham and Matthews rifle, two by George Piper (both on display at the KRA) and several by Nathaniel Rowe, but none by John Blackburn.
Does anyone have any information about John Blackburn? Where did he work after his apprenticeship, any guns known?