A C402 forward right baggage door opened after takeoff; even though it appeared closed during preflight inspection; so the Captain returned to land.

Narrative

I walked out to the aircraft and started a normal preflight walk around. I made sure (as I always do) to check that all passenger and baggage doors are closed and secured by a visual and tactile inspection. Once the walk-around was complete I continued with my preflight and checklist duties as the passenger was loaded onto the aircraft. Once the passenger was loaded the ramp agent closed the rear passenger doors and started his walk around. Like normal I made sure the ramp agent inspected all passenger and baggage doors were closed and secured. Once the ramp agent completed his walk-around he gave me a twisted fist signal and thumbs up. I then proceeded with the engine start and taxi to the active runway; and took off as usual. On my climb out the right nose baggage door opened. I made sure I still had positive control of the aircraft and continued a climb to pattern altitude. I notified my intention of landing to the Tower Controller and they immediately cleared me to land. Once established on the downwind portion of the traffic pattern I called operations and notified them of my return and briefed the passenger on the situation. I then proceeded to land normally eight minutes after takeoff. Once on the ground and parked; I wrote up the aircraft for the malfunctioning baggage door; and called maintenance and dispatch. The nose baggage doors of a majority of our Cessna 402 fleet do not have any warning system to indicate they are properly closed like the passenger doors do. A non mechanical system to insure the security of the nose baggage doors is needed. A simple solution might involve a series of alignment stripes on hinges; doors; and latches. The visible alignment stripes would be similar to those found on jet aircraft cabin doors. This would insure the doors are properly secured and not misaligned in any way. There needs to be a solution that does not rely on the worn mechanical parts of thin sheet metal doors; latches; and wing nuts to prevent this dangerous situation from happening.