Thanks for the welcomes

and keep the advice coming.
To answer some questions:
I disassembled to check for cleanliness and re-oiled before I fired it.
All parts that make the upper receiver/barrel assembly appear to match. Frame, barrel, both Toggle sections, the ejector/extractor, firing pin....you name it. The only marked pieces I believe aren't original to the gun are the Takedown Lever and Sideplate.
When it was reblued the siderails and bearing surfaces weren't spared. The bluing is beginning to wear at certain areas from action operation though.
When the cannon is assembled to the upper receiver, there is no evidence of binding and feels "good". In fact, there is no evidence of binding in any moving parts at all.
For now I'm thinking that a Wolff spring kit, and if necessary, VERY conservative use of emery cloth on the rail bearing surfaces might get this to a reliable shooter.
Anything else?