What was found
(CAN) DURING CLIMB, THE F/O OBSERVED THE R2 SLIDING WINDOW WAS CRACKED. THE DECISION WAS MADE TO RETURN TO BASE. THE AIRCRAFT LANDED WITHOUT INCIDENT. THE R2 WINDOW ASSY WAS REPLACED IAW MM 56-12-11 AND CHECKED SERVICEABLE. THE R2 WINDOW HEAT CONTROLLER AND TEMP SWITCH WERE CHANGED AS A PRECAUTION. FUNCTIONAL CHECK WAS CARRIED OUT SERVICEABLE IAW MM 30-41-02. NO FURTHER PROBLEM DURING SUBSEQUENT FLIGHT.