The pictures below show the differences between the Model A, early Model B, and late 1932-34 Model 40/46 front brake operating wedge studs. Left to right is A-2051 used on Model A's, B-2051-AR used on early 1932 Model B's, and B-2051-B used on late 1932-34 Model 40/46.
The A-2051 and B-2051-AR are functionally the same except the Model A version used a round washer design whereas the later designs used an oblong washer shape. The B-2051-B is the same as a B-2051-AR except it is 1/16 inch longer in the shoulder area that fits in the lower roller track.
The late 1932-34 B-2051-B design on the right shows the longer length of the shoulder which engages the lower roller track riveted to the backing plate.
The Model A and early Model B roller track thickness is 0.250 inches, whereas the late 1932-34 Models 40/46 roller tracks are 0.310 thick. The differences in the wedge operating stud shoulder lengths correspond to these differences.
Pictured above is an NOS early 1932 Model B style front backing plate with the thinner 0.250 inch lower roller track. The roller track is the same as used on Model A's.
Pictured above is an NOS late 1932-34 Model 40/46 style front backing plate, showing the deeper stamped depressed area around the lower track plate and the thicker 0.310 inch lower roller track plate used in late 1932-34.