I was under the impression that the characteristic mushroom-shape, coupled with the transverse-oval filament, was to create a superior light distribution to that of the more common double loop. Shelby`s famous bulbs emit more light in the downward direction and less out to the sides- more efficient pattern for pendant fixtures illuminating a dinner table, etc.
I have seen the "other" shape Shelby too. The remnants of the Past-Technology site still has a foto of a green S-shape Shelby bulb, on top of this page:
http://www.angelfire.com/pe/pasttech/l1900.htmlThere is also a Shelby advertising envelope featured here on Tim`s site:
...which is where I remember seeing about the different shapes first. Knew it was somewhere nearby!
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