The diameter of the globe depends on the oil company and the year in question. Generally speaking 15" globes were used on visable pumps, so were one piece glass, 13 1/2" glass, plastic bodied globes, 16 1/2" metal body, and 12 1/2" glass. Visables were made into the 50's I think. Let me know the company you want to do and an approxamate era, and I'll see what I can find out.
Bob
Wanted: Gas pump globes:Sinclair & affiliates, IL companies. Ripple bodies. Anything Sinclair, Stoll, Pierce, 4 Bros.
http://www.lastgas15.com/