That's a very nice PPK.
Previous posters telling you 1940 ish are likely correct, ditto the Police markings. Nobody seems really clear on the meaning of "C" (or alternately "F") next to the Eagle indicating Police acceptance. The people who were there and could have told us are long dead.
As far as what it's worth, modern (Ulm) PPK pistols are now selling for over $400, quite quickly, both here and on retailer's sites. People trying to get much more than that will wait a long time.
Given the condition of your pistol, the 12(7) potential, and the nice grips, I'd at least double that. I presume the white stuff is crayon or something to highlight the markings, and not some sort of epoxy appliance paint? After you clean off the white stuff, not a penny under $800.
Waltherforums (dot) com is good, and somewhere in my library is a three volume set on the Walther pistols (Rankin) which is interesting and of good quality. The Blue volume is PP/PPK only, and doesn't shed much more light on your pistol or its markings than has been provided by others so far. The Marschall book Walther Pistols is sometimes skinny on details, and says the same things you now already know.
Guesses as to price in the USA are both wrong (sorry) and misleading. The PPK is specifically prohibited by name in the 1968 gun control act, as is the import of former Military or Police weapons from other countries, so this one is double-banned. Those smuggled pistols (after 1968) or bring backs (before 68) fetch some pretty stupefying prices, and in the condition yours shows, at a good auction, $2000 plus. Sure, there are legendary cases of a local gun shop owner selling one for $300 because he doesn't know any better, but those are fewer and fewer.
Unlike our geniuses, the Americans banned the gun's IMPORT, not the gun, making the ones in the country immediately more valuable, and encouraging a local firearms manufacturing industry. Here, in typical British fashion, they created "classes" of people, some more equal than others. If you are in the right "class", you can own this pistol. Arguably, in Canada your property is less valuable due to the law, and firearms manufacture is discouraged.
Aside from the fact that this is an heirloom and hence priceless, they simply aren't making Pre-46 pistols any more, and you can't import them. There is a finite supply. Yes, 12(6) holders are now fewer than 40,000 individuals, but something people often overlook is that you can own a firearms company, and the company can own 12(anything) class firearms. Plus suppressors, with the right "class" of license. It isn't a trivial cost, but it isn't like buying a car either. Once owned by a company, a 12(6) such as this one can only be sold to another company, never an individual again. But if someone without a 12(6) on their PAL really wanted to preserve these, or own one without a caliber change and barrel extension, they could either be given one by a "blood relative" or spouse -- 12(7) -- or go the company route. A company never dies, has arguably better property rights than an individual, and can be owned by almost anyone.
If you like lots of old stuff, you could also start a museum. That's more work, in my opinion, though potentially more socially acceptable in our heavily engineered, Progressive, self-disarming society.
There are still other options, but by now you're probably getting bored.
In short, if you can read this, you can own a PPK just like our OP's, if you really want. No 12(6) required, just varying degrees of effort and cost, depending on whether you want to marry for one, curate one, or be entrepreneurial...