Can anyone offer info about the maker of a bottom bracket shell on a 1970s bike I recently bought. Bike has pure French tubing dimensions and French threading. The BB is fairly simple (no fancy feature-cuts like a Nervex Pro) and has "RGF" within an oval, cast/forged onto the top left side. The rest of the lugs on the bike appear to be a Prugnat "Professional" set with long spearpoints. I'm sure I had once seen this BB logo on another bike, but cannot now find an example on any of my other French bikes.