What the heck is this and do I need it?

[mgm60]

So as usual I started on one thing a ran into a few others. While replacing my radiator I saw some rust in the core support below the battery. Took the battery tray out so I could get to the rust and then see this canister, which is connected to nothing. Is this smog related equipment and do I need it or can I take out and save as a keepsake of the journey to replace the radiator (new thermostat, new radiator, new hoses, new radiator pads, repaired rust in the core support and repainted the battery tray). I though I was gonna have this licked in two hours, two days ago.

Mark