I've been watching the auctions for some adjustable sights for a K frame I have. One of the sellers has a "square front model" sight that he says fits K,L & N frame guns. I was under the impression the N frame took a longer sight, is this correct. Thanks

The K & N frames take the same sight. There are different lengths, some go to the front of the frame and others are as much as 1/4" or so short. This depended on period of manufacture. I suspect it was a cost cutting feature to use the long base sight as with a short sight the front of the sight groove had to have the matching striations cut, where with the long sight the sight groove was smooth since the grooved sight base covered all of it.

What you need to watch for is the sight base screw position. The screw was originally directly over the barrel-cylinder gap, and sometime in the 1970s it was moved forward about 3/16". The sight base screw position needs to match up with the hole in the frame.

One hint. Don't be too anal about getting a sight with the right blade height for your gun. All bases are identical (except the screw hole) and you can buy a sight kit the correct height to replace the blade if necessary. Think about it as buying just the base when looking.