A molded case circuit breaker includes a clear viewing window through its top cover to enable the position of its internally disposed separable electrical contacts to be externally visually discerned. A manually engagable handle extending through an opening formed in the top cover of the molded case of the circuit breaker has an electrically insulating strip or barrier secured thereto and movable therewith for covering the clear viewing window when the separable contacts are in their CLOSED position to prevent smoke and other arc products resulting from circuit breaker interruptions from obstructing the clear viewing window. The viewing window may be inserted in the top cover during the molding process or may be subsequently disposed in the top cover in the form of an insert fixedly secured thereto.