At some point Bulova Accutron 214 movement got a Calibre Numbering System Change as follows Accutron 214 = 2140, Accutron 214H = 2141, Accutron 214HN = 2142 And a forth Calibre 2143 was added, Although I've never seen a 2140 movement because the Swiss never made a 214 without a hack spring...
Here is one of the Swiss made Accutron 2141 movements I just recently acquired, It's an N6...
Also, Only the Swiss made Accutron 214 movements got the caliber number change which happened around 1970ish and all the USA made movements continued on with the old caliber numbers of 214, 214H, and 214HN until the day the 214 line of watches was discontinued in 1977...
For more information about the where, when, and why please visit
http://accutronfacts.freeforums.net/thread/304/accutron-calibre-numberi…