[Bird911]

You are correct, 911/41 was used in 75, and the third digit ''6'' in 6160048 mean this is a 76 serial number.
The only explanation I see is since you have an early serial number (0048), maybe the factory still have some unused blocks printed with 911/41 at the end of the '75 production, and decided to use them for the first production of '76 cars.

This is still very mysterious...