we just purchased a 1940 plymouth coupe and noticed the left tail light has a clear bubble and are wondering what function it has. looks like lots of possibilities for our new,old car and converting it to a street rod.
Ths bubble on the left tail light lense is to catch light from approaching headlights and light up the rest of the lense. Stand some distance behind yor car at night and shine a high intensity flashlight towards the bubble.
The right hand side lense should be plain. This always brings forth some discussion at shows.
My 40 is a bone stock original with 74 000 miles, never painted upholstered or rechromed and it is a wonderful car to drive compared to other cars of the era. The addition of an overdrive would make it perfect in my mind but less than perfect in show judging.