Chronometric Tachometer / Disk Speed Indicator BS Mk15 for Testing Norden Sight F-100 type AN-5825-7

type AN-5825-7

and the Turn & Bank Indicators

such as the P-40

So it is possible that there is some connection there

A Yellow (Minus Blue) filter is attached

Chronometric Tachometer / Disk Speed Indicator BS Mk15 for Testing Norden Sight F-100 type AN-5825-7Here 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.