Lamps are kind of confusing, diameters are spec'd in eighths of an inch. Consider 60A17, 25T10, even F40t12, watts, shape, size in eighths.
But then the base isn't part of the number. It's a metric "normalized" dimension, Edison didn't define the E26 base as an Edison 26mm, it was an Edison 1". An E17 was a 5/8" intermediate base, and an E12 was a half inch candelabra base.
The glass on your bulb lacks a neck, I don't think it's a "G" Globe format, I think it's an "S" Sign format. So if 1.25" lamp in watts/shape/size format would create a 40S12. I'm guessing the base is bigger than 1/2", so it would be a 40s11.