TACHOMETER, HAND HELD, 16-20K RPM (inspection), wheel is US507698
This part features three ranges, all changed via the knurled head:
16-200RPM (5-60FPM) read scale directly
160-2,000RPM (50-600FPM) multiply scale reading by 10
1,600-20,000RPM (500-6,000FPM) multiply scale reading by 100 (DEFAULT)
AMN-09/08/05