This is a tubular key from Southco, used for their specialized E3 Series Small Size panel latches. Made of stamped/machined steel with a chrome coating for protection, these keys are pretty hard to break, but not impossible to lose!
Note: These keys look a LOT like the Southco E5-5-15 but they are not interchangeable! Using the wrong key in a Southco lock could damage the tumblers in the lock and cause irreparable damage.
If you're not sure which lock you have, or which key you need, please call us or email us, and we'll gladly help you determine the right part number.