Worrest did indeed invent the trigger and owned the company that made them. Ithaca offered the Infallible single circa 1915 ish. I think James Tyson did a bit on this trigger in a DGJ article. A notch has to be cut in the top tang and I would think any engraving on a factory job would accommodate this notch. I had an Ithaca Lewis with after market installation as the engraving pattern was cut through.