Check out:

http://www.mir.com.my/rb/photography.../om2/index.htm

You'll find more information there on the 2 and 2n than you'd ever think you'd need. One of the differences between the 2 and 2n is that the 2 will meter a scene up to 60 seconds whereas the 2n will go to 120 seconds. The pages that start at the link above list all of the differences, large and small.

Be well.
Dave