This is the one-way valve that is at the bottom of the pump tube. It is a spring-loaded valve that opens when the pump tube is pressurized, allowing air into the fuel tank. The spring then pushes the valve closed on the return pump stroke. NOTE: this is the same valve used in the #2412 Brass Pressure Stove.
This valve can be removed and installed using a large flat head screwdriver. For better sealing, a lead washer is used. The lead washer de-forms when the valve is tightened for a good seal. If you remove the valve for any reason, it may not seal properly when you reinstall it because the lead washer is intended to be used only once. Unfortunately, the manufacturer does not offer the lead washer as an individual part, so you will then need to purchase a new valve, which includes the lead washer. Some customers have reported success using a fuel-resistant epoxy sealer instead of the washer.
