Jeremy,
I?ve spoken with another collector with knowledge of vintage fluorescents.? It would appear that your lamp is postwar, made after about 1945 at which time the ?MAZDA? name was dropped.? Brass bases were used on fluorescents from about 1938-1942.? For a short time during WWII, steel replaced brass.? An earlier lamp from this period should be marked with the MAZDA name.? Brass was used again after the war, probably for a short period of time before aluminum was finally adopted in 1950.? If your lamp is not marked "MAZDA", then it was probably made after 1945.
Below is a crude timeline I've made up.? If anyone has more information to add, or correct, then be sure to let me know and I'll update this post.
1938
? ?|
? ?|----------Lamps marked GE MAZDA, WESTINGHOUSE (or circle-W logo), MAZDA,
? ?|----------or HYGRADE with brown colored insulators and crimped brass ends.
? ?|
1942
? |
? |-----------Zinc plated steel replaced the brass bases during WWII.
? |
1945
? |
? |----------Brass and brass plated bases were used again.
? |
1950------Aluminum bases were used.
Thanks to Rick Delair for the info