I'm am currently trying to find when order codes were put into use by General Electric and Westinghouse.
For General Electric, I have found this Q1 1960 F25T12 in
@Marcel1968's gallery
https://www.lighting-gallery.net/gallery/displayimage.php?album=search&cat=0&pos=2&pid=244401And also in his gallery, this 20W lamp made in the Q3 of 1959
https://www.lighting-gallery.net/gallery/displayimage.php?album=search&cat=0&pos=3&pid=214078----
For Westinghouse, I have found in
@Foxtronix's gallery, this 1957 Sylvania F20T12/B
https://www.lighting-gallery.net/gallery/displayimage.php?album=search&cat=0&pos=1&pid=45099However, I have not been able to find a picture of a 1956 Westinghouse fluorescent tube yet...
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If anyone could help me find a picture of those lamps, I would really appreciate it!
