Circuit interrupter with covered accessory case with accessory having lock-in feature and pull tab

A molded case circuit breaker is taught with a housing base and a primary cover disposed on the housing base. The primary cover has a recess therein for an auxiliary module which is disposed in the recess. A secondary cover is disposed on the primary cover for covering the recess when the auxiliary module is disposed therein. In order to secure the auxiliary module underneath the secondary cover in the recess of the primary cover, the module has deposed thereon a locking protrusion which is complimentary with a locking opening in the primary cover. The locking protrusion is flexible and has a longitudinal central bulge so that as the protrusion is pressed inwardly into the opening, the bulge causes the flexible protrusion to reduce diameter due to the presents of longitudinal slots therein until the bulge has passed the opening in which case it springs outwardly toward its normal position thus securing the protrusion in the base. A flexible pull tab is provided for displacement under the auxiliary or secondary cover so that when the auxiliary or secondary cover is removed the pull tab may be tugged upon to remove the module from the primary cover by providing the reverse operation to the insertion operation previously described.