I am in the middle of restoring a 1668E engine and I realized that there is only one nameplate on the left side of the engine and nothing on the right side. There are no signs that there ever was one either, no slots for the mounting tabs, nothing. Does anyone know the Lionel history behind this? Why did this happen?, how many were made?, was it an "oops"?, what year were they produced? , etc. I can't find anything online other than some folks acknowledging that they've seen the "one-sided 1668E".
I have attached some photos of the body. It is the heavier 1668 casting with the firewall in the cab if that helps...