This is a small fuel canister/tank made of brass. It allows you to carry some extra fuel when you are going out for a trip or camping. So you can use it to refill your petrol lighter or make fire.
The canister's cap attaches with a keychain ring, you can easily attach it to your keychain or backpack.
The size of the canister: 6.3*2.2*1.3cm (2.5*0.9*0.5 in)