BudsGunShop.com - Nickel or stainless.

It is Nickel plated. The slide is alloy.

The slide is "alloy" (Steel attracts a magnet this does not) but this pistol has a Factory Nickel Plated Finish. There does exist a solid stainless version though. thetruthaboutguns.com/2013/10/jeremy-s/gun-review-walther-ppks-22/

I suggest calling Walther and asking 479-242-8500 EXT. 507
customerservice@waltherarms.com
Customer Support
all the sites list it as nickel UPC: 723364200267

Description: WAI PPK/S 22LR PST 10RD N FS
Brand: Walther Arms Inc
Model: PPK/S
Type: Pistol: Semi-Auto
Caliber: 22LR
Finish: Nickel
Action: Double Action
Stock: Black Plastic Grips
Sight: Fixed
Barrel Length: 3.26 Threaded
Overall Length: 6.06
Weight: 23 oz
Capacity: 10+1
# of Mags: 1
Safety: Manual Safety, Drop Safety
********Receiver: Nickel, Alloy
Features: Blowback Action, Threaded Barrel;
Alloy Construction