I don't know much but based off the research I've been doing on my own clock I can tell you that the "N" with the circle stands for NAVY and the number next to that is the lot number for the order from the navy in which your clock was in. Based off the serial number, your clock was originally sold sometime between 1935-1939. Here are a couple of websites you can check out that might help you with identifying more information about your clock.
http://www.chelseaclockmuseum.com/index.html
http://www.chelseaclock.com
for a small fee of $35 you can order a certificate of origin that will tell you who the original purchaser of your clock was and several other details about it.
Good luck in your hunt for knowledge!!!
Let me know if you find anything more as I would be intrested in hopes for getting more info for my clock as well!!!