Voodoo - Looks like you've got the sight thing figured out. My PM9 is also the old style - it's 9 years old. Mine has the dimple on the underside of the slide, so it's the new dovetails.
Mine is also the DLC finish. The only marks on it are inside the slide where the recoil spring sits. The spring(s) wore off a ring of the black finish, but it's not visible from the outside of the gun. The DLC finish is really tough. I wouldn't hesitate to buy another Kahr with that finish, but I won't buy one that is cerakoted. DLC > cerakote for durability.
Here's some recoil assembly knowledge for you:
PM9s have 3 types of recoil assemblies.
Type 1 is the oldest, and has a 13 coil outer spring that is rated at 18 lbs. The flange at the back end of it measures 3/8" in diameter. PM9s that use this type have the blunt nose slide.
Type 2 is the next oldest and also has a 13 coil spring rated at 18 lbs. The flange on the back end measures 1/2" on this type, and the PM9s that use this type also have the blunt nose slide.
Type 3 is the newest style, and uses a 15 coil spring. The flange is 1/2" also, and this type is the one used on the current PM9 with the taper at the front of the slide (like the CM9).
I just ordered a type 2 RSA from Kahr, and it came with a 15 coil spring. It fit, but it was a disaster in operation. The spring was really bound up on the sleeve it mounts on. The guide rod would bind up and not retract fully into the slide when racked. After a good sanding and polishing of the sleeve, it got better, but still would bind up and not fully retract into the slide when racking it. The slide also would not lock back on an empty magazine. I finally cut the spring down to 13 coils, and it works fine now. I fired 100 rounds through it, and it operates like new. My PM9 has 5100 rounds through it, and I replaced just the outer recoil spring at 2500 rounds (just because). My LGS recommended this, and ordered just the outer spring from Wolff Springs.
Wolff makes the OEM springs for Kahr. I just ordered a couple sets of recoil springs from Wolff recently, as it's a lot cheaper than buying a whole new assembly from Kahr. Their spring kit includes an outer recoil spring, an inner recoil spring and a factory power striker spring - all for $8.99 per kit, and $3.99 shipping. You can take the guide rod assembly apart and replace both inner and outer springs, but I don't. I just replaced the outer spring (factory 18 lb), and it's the correct 13 coil spring for the old style slides. I don't think you can buy just the recoil springs or kit from Wolff for the type 3 slide PM9s as far as I can tell.
https://www.gunsprings.com/KAHR%20AR...1/mID29/dID340