My Grandfather tells me that this is an early tester that you would lower into the station's tank. What can any of you tell me about it?

Thanks in advance for your help,

Jenny


DSCN1063 by JennyWren226, on Flickr

I believe that you would lower a specific gravity hydrometer in the gas sample, collected with the metal container, to detrmine quality. A lot of states requied the specific gravity of the gas sold to be posted on the pump, Wisconsin for example.
You seem to be missing the most important part, however.

I may have it and not know it, I'm sorting through TONS of station stuff. Can you tell me what I may be looking for?

Tank Water sampler, used at Bulk Plants.
Was lowered into tank & when it hit bottom a sharp jerk on rope/line would pull the cork/stopper out to let in liquid.