Interesting to see that such "rudimentary" lamp was produced for so long. GE's fluorescent tube, released in 1938, was supposed to compete with these Lumiline lamps, and we all know how successful those F tubes were!

Agreed, I suppose the nice soft glow these tended to give off made them good for accent lighting even though their efficacy left much to be desired. So they persisted for years after fluorescent tubes got introduced.

I remember reading about the early development of the fluorescent lamp and the early literature sometime referred to them as fluorescent lumiline lamps.

GE did use its Lumiline lamp platform in the early days of the fluorescent tube development indeed. This is particularly apparent in their first patent on that technology (Inman, 1936):

Interesting, I wonder if any of those early lamps survived in collections somewhere. I suppose you would have had to instant start them as well as you can't preheat the cathodes.