I have read discussions here and there were some people have claimed that Bulova never made a Mark I and in a way they didn't but this never made any sense to me, I mean why would Bulova start with the Mark II and and not the Mark I ? well that's because the first "Marine Navigator" was a experimental prototype Bulova used as a proof of concept and was the first in a line of marine timekeepers to be made, In the beginning (1966) Bulova wasn't even thinking about the next "Marine Navigator" to be released, heck they hadn't even released this one yet so there was no need for a "Mark" anything, Officially this marine timekeeper was called the "Model TE-18 Navigational Timepiece Experimental Model" which is a bit of a mouth full, This new marine timekeeper was only identified by the dial which simply said "Bulova Accutron" on it, not a real catchy name for this new marine timekeeper but that would later be changed to "Accutron Navigator Mark II" for release to the general public (1967), How many were made and how many may still exist is unknown but I know of only one ! It is currently owned by Chris Hooper of Windy City Watch Collector who runs the web site Windy City Watch Collector: Vintage Watches, Chronometers & Military Timepieces for Sale, When it went into production it was very much unchanged from the experimental prototype used for testing and from what I can tell the only thing changed was the name. Suffusive to say among the "Marine Navigators" Bulova produced it's the holy grail for collectors !
OK I do see in the Bulova advert for this that they did indeed call it the 'Bulova Marine Navigator'