I'm restoring the turtle deck on my '13 roadster, and decided the lid must come off to get it painted properly. I was going to make new hinge pins thinking they would be 3/16". Turns out they are .192"! What kind of a crazy size is that? That is about .005 larger than 3/16!
It is a possibility that it is a standard wire gage, British Imperial or English Legal Standard Wire Gage. Number "6" gage wire is .192.