Sylvania GTE f20 lamp

I found this at hab yesterday (more pics coming later.)
I have a nos one of these, with the same datecode, found at the same hab but months earlier. This one has had use, but looks to have much life left. This one and the nos one (which was slid into an empty GE sleeve) are of the same date code. I also found a rare ish 70s or 80s 32w t10 circline named ring of lite made by Abco.