Multiple choice?
******* Not Otherwise Provided (for)
******* No Operation (computer processor instruction)
****** National Organic Program (USDA)
****** Notice of Preparation
***** Noordoostpolder (formerly Noord-Oostelijke Polder)
***** Not Our Problem
**** Nuclear Operations
**** National Opinion Poll (UK)
**** Naval Operations
**** Normal Operating Procedures
**** Normal Operating Pressure
*** Net Operating Profits
*** Not on Planogram (target)
*** Nobody On Patrol
*** Nuclear Ordnance Platoon (USMC)
*** Nuclear Operating Plan
*** Noord-Oostelijke Polder (now Noordoostpolder)
*** Net Orders Processed
*** Network Output Processor
*** Navy Objectives Plan
*** Navigation Operating Procedure
*** Non-WIS (WFP Information System) Payment
I'm guessing they're some guy's initials.
Either that, or "Nuclear Ordnance Platoon"..
