This auction is for a Jaeger portable tachometer that was used by the US Air Force during 1943 in World War II. It has some calibration test sheets with that date. It was made by a Jaeger Watch Company and has a couple of extra bits. The unit appears to be functional, but it’s sold as is as I can’t fully test it. it appears to be responsive, but accuracy is unknown. The unit is in very good condition appearance wise. The box has a few scrapes and small defects. The front latch is brass and doesn’t close real well at this point. I think you could adjust it with some trial and error. Please check the photos closely for complete details.