I own several Walther PPK pistols. The PPK has wrap around plastic grips that cover the back of the pistol. The backstrap is cut away and the plastic grip actually forms the backstrap. The .380 magazine capacity for the PPK is 6 rounds.
The PP and PPK/S have a heavier steel backstrap and two piece grip panels. The PP and PPK/S have a 7 shot magazine capacity in .380 caliber.
The PPK/S is a Walther PP frame with a PPK slide/barrel. The slide/barrel of the PP (Police Pistol) is longer than that of the PPK (Police Pistol Kriminal - like the terminology of Detective Special here in the US).
Here is my pre-WWII Walther PPK .32:
Here is my 1968 Walther PPK .380:
Here is my 1988 Walther PPK .380 made in the USA at the Ranger, Alabama plant and distributed by Interarms:
I carried my Interarms PPK for 20 years. I qualified with it every year and shot it for fun with thousands of rounds. It has served me reliably and never jammed. Full metal jacket rounds, Winchester Silvertips, and the new Hornady Critical Defense ammo have all functioned perfectly in the gun.
When I bought a Ruger LCP, I retired my PPK and had it engraved with 75% coverage American Scroll by Michael Gouse. I absolutely love my Interarms PPK. I have since sold my LCP and I now carry the S&W Bodyguard .380 pistol as it has the same capacity as the PPK, but is obviously thinner, lighter, smaller, and has a laser. My Bodyguard is now 100% reliable with fmj and Critical Defense ammo after 400+ rounds fired.
But I still love my PPK for the same reasons you do.
I think the price you're looking at is a very good deal. The Interarms guns are very desirable due to the problems the current S&W production guns have experienced.