Waffenamt Mark 359 makes more sense, I researched the number you first gave 569 and it didn't compute. Military acceptance marks of E/359-E/AaA359 was first used in 1940/1941. You may want to change those grips if you continual shooting the gun, they are fragile and the grips alone will bring 250 to 300 dollars
Value, , the prices are rising on all WWII items, especially the Walther's with correct markings. If the holster is correct and the gun looks to be in good condition, I would guess 1200. However that is just a guesstimate on my part, others my have a more current estimate. If it were mine I would stop shooting it, but that is just me.