Those could be foundry identification or they could be mold markers.
The only real difference between a type 7 and a type 8 plane is one has and "S" foundry mark and the other has a "B" foundry mark.
These markings appear at different times in the manufacturing of planes. Sears even had part numbers on some of the tools they purchased from the different makers to identify who made their Craftsman line.
jtk
"A pessimist sees the difficulty in every opportunity; an optimist sees the opportunity in every difficulty."
- Sir Winston Churchill (1874-1965)
Is the sole flat or corrugated? I'm not aware of Stanley ever denoting a corrugated sole anywhere, but that doesn't mean that they didn't.
Blood, sweat, and sawdust
Flat sole.