'48 starter question

[Trekster]

I was thumbing through the Chev's of the 40s catalog and ran across a picture of the thing on my starter. It is a polarity reversing switch. The reversing switch reversed the flow of current through the points each time the truck was started. By reversing the flow it would cancel out the transfer of material from one side of the points to the other. Chevrolet used these from the early '40's to April of '48 which might explain why my other '48 does not have this switch.