When I saw the big shiny "S Biggin & Son" medallion on this saw my crow like instincts kicked in and I whipped it out of the saw bucket it was hiding in. Glancing at the split nuts, lambs tongue, blade stamp, $3 price tag, all confirmed that this saw should be added to my increasing pile of saws. It was only later, when I was doing a more thorough after-sale inspection that I realized that the blade stamp was "R Groves & Sons". [I assume that the medallion, or the entire handle and hardware, were a later marriage to the blade, and that Biggin never used Groves blades in his saws]. The blade has a nice rounded toe, but the 19-1/2 inch length is a bit suspicious. Unfortunately the steel is pitted and a dull grey that suggests its been cleaned with acid or electrolysis, but the name stamp is quite interesting; I've not seen such small lettering before. The "Groves" letters are only about 1mm high, "Sheffield" letters up to 2mm high, and the "USE" trident is tiny.
The handle looks like the BIGGIN. One son 1845-1849. From HERE. Not so much like your Groves panel saw. Toby