I might postulate a theory about the possible origins of the hood/bonnet stamped "165-2."
It has been established that during the body production process certain individual removable items are fitted, stamped with the last three digits of the body number, then removed for separate painting. During the final assembly process they are reunited with the body, the body stampings assuring that they are reunited with the correct body.
My theory is that the original hood/bonnet for the body 165 then in production was damaged in some way during the paint process, while in storage awaiting being reunited with the body, or in final assembly. During final quality control check this damage was noted and the car was sent to the rectification department. There a new, untrimmed hood/bonnet from parts was fitted, marked 165-2, painted, and united with the finished vehicle. The quality control and rectification process complete, the car was released for shipment.
The existance of two hoods/bonnets, one marked 165 and one marked 165-2 in the rectification department would be the proof needed to justify charging two hood/bonnets to one vehicle during the assembly process to accounting.
How it came to be fitted to your car is likely as a result of a body shop needing to find a used hood/bonnet to repair some past collision damage to your car.