I did look through my limited resources, but did not find anything that looked like "it". Besides the apparent long wheelbase, it seems that the bottom edge of the sheet metal is lower than on other sheet metal trucks.
Two things, to me, are of interest: what is this truck, and why is it running in 1938
This car appears to be being used in a train in mainline service.
I thought sheet metal trucks were long gone by this time.