Have you got the Mil-code right? Isn't it 46374E instead of 43674E?
I'm not sure I can help you with the movement. It's swiss. Maybe it's a ETA2801. According to Country Comm
http://www.countycomm.com/490DESCRIP.htm
the mechanical model 490 by Stocker an Yale is powered by that one.
Maloja at Ebay
http://cgi.ebay.com/US-GOVERNMENT-MI...QQcmdZViewItem
claims the same (bought that one overpriced for my wife and she loves it). But both says the movement is high-beat at 28000 bph, not 18000 bph
The best resource I've read on Marathon and the mil-codes is this though
http://home.earthlink.net/%7ebrendo81/46374.html
But I can't remember the movement being mentioned.
Have fun.
Cheers Henrik