To add to the previous excellent replies... most Super Foxes built on the heavy 0-frame will measure about 2.440" across the breech balls (fences). That width would be the average of measurements, with a small range of variation plus/minus.
With that said I've owned and seen a very small number of genuine Super Foxes built on the regular size 12 gauge frame (approx 2.350" across the breech balls). It seems the regular frame was used when the SF was ordered "light". All these regular size guns carded as HE grades, and had the H stamp on the water table and the barrel flats. I have some data to support that the regular frame size Supers were made with a heat treated alloy steel. Rockwell test measurements show significantly higher C-scale numbers than regular run of the mill 12 gauge Chromox frames.
Do all Supers have the H stamps on the water table and barrel flats? Answer: virtually all do, but I wouldn't say 100% or always. The gun's serial number, corresponding production card data, and physical measurements are proof positive. Incidentally the "H" stamping seems to be a proprietary font and special height made for Fox-Philly and Savage. A hardware store or industrial supply outfit's H die stamp will likely be the wrong size and definitely the wrong font. Silvers
