What exactly is a “S&W” action? I didn’t know that Skimmin & Wood developed their own proprietary action. A modified S&W action? What makes a S&W action different? What is a hallmark or identifying feature of a S&W action?

In my experience….the JA markings are for Joseph Asbury’s. Asbury’s probably made the entire gun. Possibly delivering it in the white or even fully finished. I can be almost certain that the action is marked with a JA as well. I’ve had various JA guns on my bench…some have Greener lever work, others have had Scott spindles, I currently own a Linsley Bros that is a JA made gun…it has a very odd spindle system in it where it uses a pin mounted in the spindle, and the leg of the top lever spring rest on that pin. Odd. I’ve never seen another like it.