Technical 46 ford brake shoe question

I have some 46 front backing plates I am using on my model a and I need to reline the shoes, I have noticed that one shoe has Ford U.S.A BB (first B reversed) the same as is stamped into the backing plates, but the other three have Ford U.S.A. K stamped into them and seem to be made of thicker steel and have three flats pressed into each side to correspond with where they touch the backing plate, are these just a later replacement shoe or are they the wrong ones ?

 

anyone familiar with these ?

 

I'm pretty sure that all are original Ford and that the letters represent different suppliers.
Ford probably used more than one spplier '46-8 and quite possibly several others after 1948 as batches were produced for parts department sale. If they fit the backing plate, I don't think they could be wrong parts. Earlier Ford was different in fit, other Locheed brake stuff woud have been non-Ford for Chrysler or whatever.

 

Thanks very much Bruce just the answer I was looking for.
Graham