First post...I did search but did not find the answer. Does anyone know about when the milkglass Shell clamshell globes first appeared? I realize that once out, they could have been stuck on just about any pump, but I was hoping someone has some evidence of what years/generation of pumps they first appeared on. My motivation is that I have visions of finding a pre-visible and adding the clamshell to it. I can use Photoshop to see how it would look, but if they likely never appeared that way, I might think twice.
The authority on Gas Globe identification, history and value is the PCM e-book "Gas Pump Globes" The 2020 edition says that the most common shell shaped milk glass globe with embossed "SHELL" lettering was used from 1931 to 1960. It is possible that a non-visible curb pump still in use in the 1930s or later could have had that globe on top if it had a provision for a globe.