This is a truly special piece! The pendant is an old style of gauge that would have been used by a machinist. Quite frankly, we don't know it's exact purpose. Even without knowing precisely what it is, anyone with an interest in old hardware and gadgets will find this cool.
The pendant is fixed to a chainmaille necklace in a foxtail weave, using gunmetal jumprings.
The pendant measures about 1.5"x2" and the necklace measures 22", including a 2.5" extender.