On most guns "Made in America" you will not find the definitive proof marks. On some you will find the provisional proof marks, but not all. none of my Lefever guns have any proof marks at all, though I know that some have the Belgian provisional marks. The provisional proof was a proof applied to a rough tube, un-finished on either outside or inside & un-chambered. Definitive proof was applied after the barrels were essentially finished & had been joined together.
My feeling is that American makers bought the tubes "In the Rough", bearing only the provisional proof & then finished them to their purpose. In the process of finishing many lost enough metal on the OD to lose the provisional mark.
If you find a set having definitive proof then that set of barrels was jointed & finished in Belgium. I cannot say absolutely that none were, but I have yet to see a set of barrels from a noted American maker carrying these definitive proof marks.
