From what I understand, farmers would get the non-ad glass pumps, and local stations would get the ad glass ones. This is what I was told by a farmer back in my hometown. But from what I've found, a lot of farm pumps had ad glass too. It may be that the farmers that I have seen bought the gas station's pumps when they were going out of business, or upgrading to newer pumps.
If you ask me, the ad glass ones are more desirable and probably slightly harder to find. I'm sure there were about as many farmer's pumps as glassed pumps.
In the end though, you really got to hope Jack Sim is around and can give you the answer. If anyone knows, it's HIM!
