I've just bought an old 1930s Stanley plane in very good condition which, after a bit of fettling and sharpening, is cutting really well, however I can't totally retract the blade, leaving about 2mm exposed and I'd like to get thinner shavings. I've had to move the frog back away from the mouth edge to get to this point and I'm a bit concerned the frog might not be original. For reference it has the raised base around the front knob and one patent notice at the back of the frog. The lateral adjust lever has 'Stanley' stamped on it. Any advice or pointers would be most appreciated.