I have found a possible match for the color called Gunmetal used on pre-1952 cars including my Mark V.
It is a 1987-95 Porsche color L699 Granite Green Metallic.
If you google Porsche L699 granite green it will come up with a lot of images.
If you have a pre-52 car or even an orphan part painted original Gunmetal, I would be glad to hear your opinion as to whether you think it a good match to this Porsche color.