This NON MAGNETIC does not actually have low MU markings and is composed of non magnetic parts that failed the military's signature testing.  These are very easily identified by the unique foil style label US Divers placed on them as well as the heavy yoke with small yoke screw.  It is reported that approximately 90% of the non mags submitted to the US Military failed the test and did not receive the low MU marking.  Some of these regulators still went into the service of the country for missions that did not require a low magnetic signature and were used in various "tactical" missions.  This model is serial number 1721, however I do know of one other in a private collection serial number 2018 indicating that perhaps over 2000 tactical non magnetic regulators were made by US Divers.