2nd Wheel Id

[barber1303]

Anyone know why these two "2nd Wheels" are different? One is from my '85 and I believe it is original to the model (bottom). The other comes from an unknown year spare transmission (top). Is this a design upadate? If so, what is better about the top design?

 

[one2dmax]

Not as much machining required and better dog slot profile on the one where they are only cut to a partial depth.