Please see my website for differences between the OM-2 and 2N.
The best difference is that ALL 2N bodies have ALL the improvements ever made to the plain OM-2 over the course of it's production. Compared to very old OM-2 (serial number 100,000 to 200,000), the OM-2N is ultra dependable. Always use silver oxide batteries (MS76, SR44, G13, 357, 303) as alkaline (A76, LR44) and lithium (CR1/3N) batteries cause lockup and meter errors (these battery types came out after the camera was designed).