(O/0 either being ctober or 0 = the 10th month being err October!) So the current mode of thought is like this. This was mainly because it was noted that there were apparently a lot of watch serial numbers with the 2nd number of 'O/0' pointing to an October manufactured Month. With Citizen Watches it was thought that the Serial number worked in the same way but it is now thought to differ with the month part. ? - 2006 Oh this year is going to be Fun!!!!!! So this watch was produced in November 2001 -)) The 2nd number or letter signifies the Month 'N' which is November The 1st number of the serial number signifies the year which is '1' so that means it is 2001 With a serial number of 1N0596 is easy to date. So for example the Seiko SKX007 Powered by a 7S26 Automatic Movement. Well it's pretty easy just so long as you know when the Movements were in production. Now I run around after my child & post less frequently!!!! I posted this quite a while back when I was still running around & posting on the forum on a daily basis.