What was found
(CAN) #1 ENGINE HAD OIL PRESSURE FLUCTUATIONS IN FLIGHT. THE AIRCRAFT RETURNED TO BASE WHERE POST FLIGHT INSPECTION FOUND AN OIL LEAK ON THE LH ENGINE AT THE EXTERNAL PRESSURE OIL TRANSFER COUPLING ASSEMBLY AT FLANGE "C". ON DISASSEMBLY THE AFT "O" RING ON THE FORWARD PRESSURE TRANSFER TUBE WAS FOUND CUT. THE "O" RING WAS REPLACED AND THE ENGINE WAS GROUND RUN SERVICEABLE.