This is an aluminum 22 cubic foot nitrogen tank with a CGA 580 valve. It is most commonly used to serve nitrogen or beer gas when pouring stouts in your draft system.
These tanks are sold empty and will need to be filled by a local gas supply company
Typically new tanks are good for 5 years before you have to retest them (hydro test). I currently have two that are due for hydro testing in 2021. The ones due in 2021 are marked down by and additional $30 to account for the cost of the hydrotest that will be due in the coming year.