Air Density Meter K and best D

Great vintage gauge -- an Air Density Meter, by K and D Accessories.
An instrument for Carburetor Jet Selection and performance testing of Engines.
Made in Burbank California.
This is a very cool gauge for racing enthusiasts.
In the original box.
Some minor wear to the finish and pitting/rust on the back.
Untested, but no reason to believe it doesn't work.
Residue on the interior of the glass.
RARE vintage air density gauge. best