Have 2 of these fixtures i found beside a dumpster over a year ago. They were F40 strips.
I recently found three 8 foot versions of this fixture which were slimline. The socket brackets are interchangeable between the 8foots and the 4 foots which has lead to the 4 foot ones becoming F48T12. The 8 footers will be tandem F40T12.
Ballasts are electronic Sylvania quicktronic ballasts for F40s but have been modified for slimline by unsoldering 1 of the red and blue wires. They run in parallel and are instant start. Unfortunately I only own 1 lamp right now. I am hoping the use of electronic IS ballasts for F40T12s at 600voc will extend the otherwise shorter lifespan of F48s at 9000 hrs