For US sellers, looks like between $750-900, with some at 'buy it now' at about $850. Note, these are asking prices, not sold prices. Value is quite subjective, depends on many factors including how interested the buyer might be. Hope this helps.
The box appears to be the original German police box with the officer's name pen-written on it. The manual is a later export version, as it's in English and includes the PPK/S, which didn't exist in 1966. The blued chamber indicates a non-factory refinish, which would be a minus for me.
Looking at completed GB auctions, a Nds-marked pistol like yours, in somewhat worse shape without box, sold for 699 recently. A Danish police gun sold for 650, but three others, also about the same vintage and clearly ex-police, for 650, 675, and 750, closed without bids. I think that gives you as good an idea of a realistic upper limit as you're going to get.
Thank you. I have the original manual also, it’s in German. I have been told that the handgun came with both an unfinished barrel and a blued barrel. Not sure how to confirm this. Thank you for your assistance.