I think that dual rear lamps were required by law in a few states during Advance-Design years (I think that Washington state is/was one example).
That's interesting.
None of the Suburbans or panels I've bought has had the dual tail light arrangement though a couple of them have had the '39 Chevy lights on the sides.
Amusing to me is that its the '48 and the '51 that came with those lights, the '53 and '55 1st did not come with them. These are the trucks I own or have owned, not a general statement about what GM was building at the time.
My driver Suburban which probably did not start out in Washington does not have the factory turn signal switch, though my other two '54/'55 GMC's and a '55 1st Chevy I parted out, all did.
Of course none of these trucks were made here in Washington, since the nearest plant was Oakland California at the time.
