My first thought was that this domain isn't anything special, but I would never comment without doing a little research.
I checked many Dnn.org possibilities, and every one was taken and many of them are actually being used instead of just being parked. Several of the ones I checked are bing used by districts, such as d83.org & d53.org.
To sell it, you should do a search on "district 74". There are 75,000 results. A good starting point to find potential buyers.
I think you will get more than registration fee.