Actually, it says P.38 (the "P." is the abbreviation for pistole). The serial number is 2888o. That is the letter o, not the number "zero"; it is called a suffix letter and is part of the serial number. German numbering started with 1 for each year, went to 9999, then 1a to 9999a, 1b to 9999b and so on.
So a full, unique description of the gun would be "German P.38, made by Walther in 1943, serial number 2888o."
The WaA 359 is the inspection stamp of the WaffenAmt (Weapons Office) inspector heading the inspection team at Walther. He served for most of the war. The three marks on the left of the slide are the inspection mark for the slide, the proof and Army acceptance mark (with the swastika) for the gun, and the inspection mark for the completed gun.
The pistol appears to be in very good condition; I would estimate it at about $800. I would like to see pics of the numbers on the magazines.