The gun was made in 1980. An order of 3000 was contracted by the NYSP, but cancelled. S&W made them available to the public. It is the only "N" frame 357 magnum revolver ever made with fixed sights. S&W did not publish an owner's manual for them, in case you're looking for one. Many of them are still NIB with collectors because of the scarcity. That's it in a nutshell. Not to be confused with a later model 520. Don't know why they used the same number.