While I know virtually nothing about petro values, I get a number of requests about the values of Model A Ford Victorias. I usually try to give a range based on my understanding of the current market, tailored by what they tell me and send me about the car in question.
Jack, I doubt that most who contact you with "three or four pictures, no offer to sell it to me" even think that you might be interested in buying the item.
I also think that those who contact you for a value quote are not going to be buying a gas pump book. They simply want to use your knowledge to see "just what can they sell it for". Your reticence to jump at these requests isn't going to make anybody mad IMHO.
Your answer "I cannot put a value an anything I cannot touch", is very valid. I don't think your approach should change.
