N0 it a fuel sucker. They worked very good when all was well. But as they aged, they failed all to often. If you want to keep them in place for originality, open them up and install an electric fuel pump inside, close it up and only you will know whats up. Iceman
Vacuum tank, as others have pointed out. This is what they used before fuel pumps. It was like a mini fuel tank with 2 chambers. Engine vacuum sucked fuel into the upper chamber, when it was full a float closed a valve that cut off the vacuum. Another valve opened and the fuel ran into the lower chamber. From there, it ran to the carburetor by gravity. When the upper chamber was empty the vacuum would fill it up again. More complicated than a fuel pump and could break down, which is why they stopped using them. If you replace one with a fuel pump keep in mind the carburetor won't stand much pressure without flooding, as it was made to work by gravity not pressure. PS they got pretty reliable, eventually. One company was going to bring out a simple vacuum tank that was sealed like a tin can for half the cost of the regular type. When it wore out you just threw it away and installed a new one, as we do now with fuel pumps. But that was about the time fuel pumps took over. That was around 1930, the most reliable pump or tank would be liable to break down or wear out after all this time.
Thanks Ice Man, and expecially you Rusty O'Toole. As TomWar said...very interesting. And I obviously learned something here. I thought maybe it was a pressure canister for one of those under-dash hand pumps.