@Craig Here is an interesting one for you. This triangle came from a early 1960's 26". It is a light color porcelain enamel. I had a visit from "The Collector" late last week and he confirmed my thoughts when I showed it to him. Its pretty cool. I'm going to take care of the rust and put it on "Pops".....
(http://i1283.photobucket.com/albums/a553/slieberman92/triangle_zpsfy84wypj.jpg) (http://s1283.photobucket.com/user/slieberman92/media/triangle_zpsfy84wypj.jpg.html)
(http://i1283.photobucket.com/albums/a553/slieberman92/triangle4_zpsawrdjjzk.jpg) (http://s1283.photobucket.com/user/slieberman92/media/triangle4_zpsawrdjjzk.jpg.html)
(http://i1283.photobucket.com/albums/a553/slieberman92/triangle3_zpscqc07ypb.jpg) (http://s1283.photobucket.com/user/slieberman92/media/triangle3_zpscqc07ypb.jpg.html)
(http://i1283.photobucket.com/albums/a553/slieberman92/triangle2_zpspgm6tjeb.jpg) (http://s1283.photobucket.com/user/slieberman92/media/triangle2_zpspgm6tjeb.jpg.html)
(http://i1283.photobucket.com/albums/a553/slieberman92/triangle5_zpsaile5df5.jpg) (http://s1283.photobucket.com/user/slieberman92/media/triangle5_zpsaile5df5.jpg.html)
I have or had an 18.5 one like that at home with similar rust showing through. It came with a 1980 B code black. I had assumed it was owner painted at some point. I'll have to see if I still have it by that i mean whether or not I have painted over it.