I found this at a yard sale and I was wondering if anyone knew what it was.
Looks like some sort of specific gravity device to check gasoline when it is delivered and convert gals with specific gravity reading to actual tanker delivery.
It's called a hydrometer and it is testing the specific gravity of gasoline at the specified temperature to ensure the proper alchohol(octaine?)percentage. There is a similar device used by distileries to check proof. We have one where I work that is used to check green liquor density. It has a thermometer and correction chart built into the center of the device.
Thanks Jim and Chester. I had no clue what it was.