That rear sight is the end result of patrolling E-Bay for about a year and a half. That particular example is a genuine S&W 745 rear sight. It appeared to have never been on a gun before. The vendor from whom I bought that one, only had one. I paid $125 for it. Pretty silly to pay that much, I know. But I like it. I think my used 645 was a LE gun. The half moon rear sight that was on it was all beat up. There's probably an old Crown Vic in a junkyard somewhere with corresponding dings in the door frame. My 645, as I got it, had numerous scratches, but they polished out. Most 645s look better than mine.
The Pachmyer grip panels were new/old stock; also from E-Bay.
The extended mag release came from Jack First.
Be careful when buying from Jack First. Some of his stuff is real factory parts. Some parts, who knows from where they came?
The difference between a Jack First rear sight and a real 745 sight is the 745 notch will be much deeper. I don't know why they made their rear sight notch so shallow. It wouldn't have cost them anything to make it deep, like the real 745 rear sight.
*The E-Bay 745 rear sight was initially too tall. Man,
I REALLY hated to take down that $125 rear sight.
But 6 inches high at 25 yards is simply unacceptable.
But the real 745 sight, with that deep notch I keep going on about, still had a nice deep notch, even after I took it down several thousands. Maybe S&W makes the rear sight too tall on purpose, so they can be taken down to zero the gun.
If you get off 5 perfect shots, you're rewarded with a good target.