If it is the double sided key then its a 2553. If the cabinet has an external handle that the lock is in its a CH751. For some reason Motherola used a different key on the 6' cabinets than on the shorter (Compa) cabinets. Unfortunately I don't have a spare, but they are made by Chicago Lock Co. and they should be able to sell you what you need.
Dan N8DJP
