Vintage Auto Parts Manufacturers Identification Mark of a Circled Offset RT

Vintage Auto Parts Manufacturers Identification Mark of a Circled Offset RT

I'm seeking the Name of a Vintage Auto Parts Manufacturers that had an Identification Mark of a Circled Offset RT.
I found this mark on the inside of the cast aluminum frame on a pair of oval Opera (Quarter) Windows with beveled gl***.

Any information on this Manufacturer or the Vintage Automobile that these would apply to, would be greatly appreciated.

Photos:
http://s769.photobucket.com/albums/**331/sysgenss03/FM/?action=view&current=FM009-11.jpg
http://s769.photobucket.com/albums/**331/sysgenss03/FM/?action=view&current=FM009-3.jpg

 

in the aluinmum and zinc die cast industry and many others these subcontracors were allowed to out there mfg mark on the pieced they shipped to the auto plants. does not mean much other then who did the casting

 

I guess what I'm really looking for is who the Mark belongs to then or better still what Year / Make / Model that these particular Opera Windows were use on.