Marker light help

Anyone have an idea what this would have been on? About 16 inches long, 5 inches wide, curved, and made from cast iron. Thanks in advance

 

It looks like a cab marker light off an older truck.

 

Thanks. I was thinking it might be of an old bus or possibly even an old train. Anyone else out there want to take a guess?

 

GM bus around '55

 

Thanks LowKat!

http://forum.bustalk.info/viewtopic.php?p=16913&sid=627b8be1898f6c234101d327059efbf2

 

This is the "Rosa Parks" bus in the Henry Ford museum.

 

You think that's a Doo Ray and that a glass Doo Ray lense will fit in there? It has a nice shape.

 

Not sure. Here is a close up of where the lens whould be.

 

I have several lights exactly the same . I pulled mine off a mid 50's GM Military bus. Cool lights