This is a Sargent type 2 #3416 (a #26 in Stanley terms. It 15” long. The body is beech. I’m going to do a restore to get it back into a respectful looking shape.
One thing I think the Sargent had going for it over the Stanley was the way the frog fastened. Sargent used steel to steel machine screws. The metal base was threaded. Stanley used wood screws here and many of them were stripped.
The cap screw on this frog was solid. There are several ways to get a stuck screw out. You see several methods being used through my writings. It possible to spray it with a good Blaster 16-PB Penetrating Oil ,Or heat them like I did here and here
But this time I just clamped it in a vice, with the jaws wrapped in aluminum to protect the head, and spun it.