Howdy again, Uncle C!
No, the tool is similar to the tool in the picture that Marshal Will posted. His is a swivel knife with an adjustable arm so you can cut a border using the "arm" as a spacer that keeps it even. You put the tool "arm" on the edge of the leather, then it cuts a very even border gouge. My tools are essentially similar, but opposite in function. The "arm" on mine has a very small cutting hole and the center shaft of the tool rides along the outside edge, which makes it all the same spacing.
I'm just a beginning leather crafter, but I have LOTS of experience "sidewalk supervising" my buddy who is the saddle maker pro. I have helped him a bit, but it's been on the metal working end of it. (I polished out some brass "Ds" and fancy conchos on a very expensive [$4500 plus!] saddle he made for one of his customers and have done other minor metalwork for him as well.)
Back when he had more time, he also built my gun rig. I have a cartridge belt w/ R&L side holsters; a set of Slim Jims that the right side can either hang straight as a strong side holster, or canted for a crossdray type; cuffs; SASS badge holder; and other projects that he crafted for me. He made a nearly identical copy for display purposes of the Menea holster that is featured on the front cover of "Packing Iron." After a couple or 3 years, he finally broke down and sold it to me. This was not long after 9-11 and the bottom pretty much fell out of the business, so he needed the money. His business (and others - especially in this area) STILL haven't recovered well.