6680-00-921-1039 (MIL-T-16049)
6680-00-921-1039 is equivalent to manufacture part number 1600-4. It is a handheld mechanical tachometer and is classified under Federal Supply Class 6680 (6680 - Flow and Level Measuring Instruments), stocked for defense, aerospace, MRO, and industrial maintenance applications. This item is cataloged in the NATO supply system under 6680 - Flow and Level Measuring Instruments and is available through NSN-PARTS for U.S. government MRO, and commercial procurement.