Okay, do the grips have a diamond in the middle, these are called the Magma grips?
Here goes, you seem to have quite a rarity here. It all started with what S&W called the Hand Ejector Models. These were target guns and are very sought after today. After this and still keeping the Hand Ejector moniker, came the 45 Cal. Model of 1950. After this came the 45 Cal model of 1955. With both of these, the main caliber was .45 ACP with very little made in .45 Colt. They are known as "pre-model" Smiths before the model number designations.
The .45 Cal Model of 1950 was the prerunner to the Model 26 a light barreled target gun. The .45 Cal Model of 1955 was the pre-model 25. These gun serial numbers started with the prefix "S", not "N" as yours is.
Your N prefixed serial number puts manufacture in 1976. As yours is a known model 25-2. Now, here comes the good part. There is a quantity of "Known" model 25's, approximately 100 pistols, that were known to be mismarked on the barrel roll marks stating ".45 Cal Model of 1950". If this is true, then you have a mighty valuable pistol there.
Now, what to do next. The first thing you should do is relagate that pistol to the safe and leave it there. Next, I would get a letter from S&W by writing Roy Jinx, the S&W historian. Give him all the information on the gun, WITH PICTURES and from every angle and make sure you can read all the markings clearly. From the serial number, he will tell you exactly HOW it left the factory. This will cost you about $30 and will be the best money you have ever spent. Once he knows about this gun, go over to the S&W forum where Jim Supica hangs out. Jim is the author of the "Catalog of Smith and Wesson, Second Edition" which I have and where I got this information. He has a forum in there devoted to information for his next edition and where you can get his attention with pictures of the pistol and detailed information that I am giving you here. I am sure he would be very interested in hearing from you and you just may get your pistol into his 3rd edition. Unfortunately he has closed the 3rd edition, but still go speak with him. You can "google" his name and you will pick him up at "Old Town Station", his business.
Also, get yourself a copy of Jim's book from Amazon.com and see for yourself. You can follow all the history of the hand ejector series of pistols.
Now, the next thing I would do is leave the cleaning kit sealed and do not open it for ANY reason. Go on Fleabay and buy yourself a S&W wooden presentation box that will accomodate a 6 1/2 inch barreled N frame. Then you will have have all the correct pieces except the original paperwork and shipping box.
I cannot guess what it is worth today, but that kind of rarity will oftern bring in high 4 figure prices, Jim would know this better than I. N frames today are highly sought after and collectable. I own 5 myself.
If you take my suggestions you should be a proud owner, if it letters out, of a highly collectible S&W N frame.
Please post pictures of it here!
Here is the S&W forum: