Chronometric Tachometer / Disk Speed Indicator BS Mk15 for Testing Norden Sight
Here is a WWII-era Chronometric Tachometer / Disk Speed Indicator Kit, made by Technical Oil Tool Co. (TOTCO), used by bombardiers and technicians to check the proper operation of the Norden Bombsight
The kit contains the disk speed indicator, two tachometer tips, instructions, and a metal case with a rubber-lined compartment.
It is in very good condition given its age. The case measures ~4.5 inches long, 3 inches wide, and ~1.5 inches deep.