This probably won't help ID this cap, but I have a thimble (why they would make a thimble to help sell a car I wouldn't know), that has this color of blue background and the same type of font for the lettering. This motometer will probably be some dealer promotion that has got to be rare, never seen another. Cool piece. Ross

Where Are You From? Orygun

Do You own a car built by Durant? 1930 6-14

My best quess is Someone really got creative, looks like they are using a Cadillac, Lucas or other marques "divers helmet" type tail light unit. The square area where they placed the DURANT type is where the license marker lens goes which at this era light would be facing downwards. The red lens that normally faced out is now mounted downwards. The two side lights lenses would have been Clear,amber or Red.
Interesting, for sure.

Where Are You From? New England

Do You own a car built by Durant? Yes a few :)