What is It? Game 19

Today's collaboration with What is It? Blog brings us this strange-looking dial. Guess what it is and win a Free Neatorama T-Shirt! Check out What is It? for more clues on today's object.

Place your guess in the comment section - please do not post any URL, let others play!

Update 4/13/07: The answer is:

Years ago fuel delivery trucks didn't have any type of a pump to transfer the fuel from the truck to the farmer's storage tank. The fuel was moved in 5 gallon containers by hand. This indicator was mounted on the truck and each time a 5 gallon can was filled they advanced it one space to keep track of the gallons delivered.

This must be easy for you guys, winner is SarahS #6.