The 1931-1932 Chevrolet cars were equipped with chrome plated oval taillights. Their attractive design added to the overall appearance of the new passenger car. This was to help attract potential customers that were experiencing some of the worst years of the Great Depression.
We find that GM reused parts of these car lights again on the 1934-1939 Chevrolet Trucks. This was the housing or bucket and some internal connection parts to secure the light bulbs. This saved GM much rather than designing new tooling for a work truck.
As repeats they were not noticeable to most because the buckets were now painted black and only the painted outer ring and lens were different.
Just another way GM saved much tooling money by passing on earlier car parts to their trucks a few years later. After all: Trucks were for work. Their appearance was secondary.
1931-32 Car Taillight
1934-39 Truck Taillight