This machined area is rather low, and has two holes that receive the screws which are used to secure the frog in place.
All dimensions that follow each number indicate the length of the sole, the width of the cutter, and the weight of the tool.
The entire frog is adjustable forward or backward to close or open the mouth, as the case may be by a set screw that is accessible directly below the frog's brass cutter depth adjustment nut.
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No model of the 2 has the patent date s cast into it, behind the frog.
A wider and heavier jack plane for rougher work.