The original type study doesn't mention it, but there are several treatments of the lever cap, where its finish and the background color of the notched rectangle follow what seems to be a 'style du jour'.
I can't date accurately when each of these lever cap treatments occured, but I can list the order in which I believe they were made: The lever cap is machined and finished as before, with the notched rectangle's background japanned.
I believe this to be the earliest since the earliest Bed Rock planes have lever caps of the same treatment (Bed Rock lever caps always had some embossing on them, and the earliest ones have the japanned background).
My experience tells me that this lever cap treatment is rather uncommon.
The screw may then be tightened, by a turn with thumb and finger; and the Cap iron will serve as a convenient handle, or rest, in whetting or sharpening the cutting edge of the Plane Iron." There you have it, in all its gorey, why the circular hole was repositioned, after it being at the top of the blade for some 100 years. However, the patent drawing for the change shows what I believe is the real reason for the change - the circular disk, on the lower end of the lateral adjustment lever, loses its ability to engage the slot provided for it (in the cutter) when the iron is nearly used up.
By relocating the circular hole toward the bottom of the cutter, the iron can be used right up to the slot, without sacrificing the advantage gained from the lateral adjustment lever. A smaller bearing surface is now cast into the bed, toward the tote.
Two circular bosses, to receive the screws are located just ahead of this bearing surface, toward the mouth.
A rib runs from the mouth to bearing surface, over which the frog rests.
All 3 of the logos are the result of the merger between Stanley Rule and Level, the tool producer, and The Stanley Works, the hardware producer. W." stands for The Stanley Works, and "STANLEY", obviously, stands for the rule and level firm.
A notched rectangle, in which the word "STANLEY" is stamped, sits over a heart-shaped design, in which the letters "S. The heart-shape is a memorial to The Stanley Works long-time president, William Hart. A." in two lines under the heart, and dates from around 1920.
A frog adjustment screw, first offered on the Bed Rock planes, is now added.
This is located below the frog, and engages a fork that is screwed to the frog.
Another tool pal of mine, from longuyland, has seen one before.