[QUOTE=sheepherder;253071Dave, can you see it???
Is it something maybe one inch in diameter and shaped to fit the cavity???[/QUOTE]
The solder joint at the front of the insert is fairly visible, and if you look closely, a seam is evident in the material b elow the newly-created place for the pin. It would appear that the unit is slipped into the cavity in the frame, and the dovetails on the face of it assure that it won't be torqued around. The closer the fit of the joint, the better the solder bond; so I'd imagine a lot of work in fitting the piece to be patched in. The concept seems simple, otherwise. Thanks for the pics Ron.
I'd like to have a 1900 shooter someday. Changing over the recoil system would eliminate any worries about breaking a flat spring. This modification is semi-permanent (could be restored with a bunch more work) but the theoretical pistol would be a shooter.
Rich, I was referring to the adjustable recoil spring guide in another thread.