Unknown Vacuum canister – 1968 Polara 500

I have a vacuum canister in my passenger front fender that I’m not sure what it does. The car is a real project, and the lines are unhooked. I was able to chase one to the engine side into the firewall, but there the mystery begins. I couldn’t find info in my Service Manual. My real question is I don’t know which line goes in what hole, but given this is my first time working on it, I thought I’d start at the beginning. Thks.
Author: PatinaPolara