There were about 1200 or so Troopers on the NC SHP at that time, so they bought enough for all of them and a number of spares. I would estimate 15 to 1600 in total (just a guesstimate)
The SHP had Model 66's prior to the 686, but kept them for a very short period of time. Both the Model 66 and 686 had the SHP Badge roll marked onto the side plate as in the photo above. One sees the 66's come up for sale more often than the 686's, even though there are probably more 686 guns.
The rarest is the Model 686, 2.5 inch guns with badge that were issued to the Governor's Security. I've only seen one of them.
As to value, I agree with colt saa. A police gun collector or a former/current NC SHP Trooper might pay a small premium for the gun. I can tell you that one appeared on Armslist earlier this week at $850 and its gone now. Don't know if it sold or was taken down. I talked to the former owner of the law enforcement supply business who sold the guns to the NCSHP and he said that the thought $850 was at the top end of the value, so I passed on it.
The NC SHP 50th Anniversary Commemorative has held its value fairly well, but that' probably because its a Model 29-2 and is the first 44 magnum commemorative and the only gun to have the "engraving" done by acid etching.
There was some "controversy" concerning the Model 686 guns as the SHP armorer who wrote the specs for the guns specified "Book matched target Goncalo Alves Grips. The guns came in with regular target grips and the SHP First Sergeant, who was quite the character, refused to accept them. S&W had to quickly make (they still had their own wood shop) 15-1600 sets of the specified grips and ship them to Raleigh. The S&W law enforcement rep and a couple of guys he hired had to drive to Raleigh and change out the grips. The rep called his boss and asked what to do with the original grips and he was told to burn them. I'll leave it up to your imagination what he told me he did with them.