I thought someone might be interested: http://grail-watch.com/2015/03/30/prototype-4-2-mhz-omega-quartz-one-of-two-made/
I know this watch well, it came from a lot of watches sold by John Othenin-Girard, the creator of the calibre 1500 family of watches, known to most as the stardust and the Marine Chronometer. About four years ago J O-G sold a number of pieces to a Swiss dealer, I bought three which included a cal 1500 prototype elephant (the only one outside of the museum) and a prototype hard metal cal 1340, this watch was amongst the lot the sold. The movement is completely legitimate and correct, guess there was just no call for this accuracy by the time it was produced, a great piece of history thought! Such a shame it was developed in a super cool case like the MQ 2.4Mhz prototypes I own