The German Eagle vs. Nazi Eagle are sometimes hard to tell apart but, depending on when it was made, most PP and PPK pistols have a marking on the barrel shroud that you can see through the ejection port, with a symbol and two numbers. The numbers (eg. "65") represent the year the gun was made.
Your slide is marked ULM, so made post-war. A large number of post-war Walthers are made in France by Manurhin and simply marked with all the German markings. In Europe, where the pistol is "proofed" (those eagle stamps) is where it is "made". Don't worry, the Manurhin PPKs are very nice, as yours is, and work excellently well. According to Dieter Marschall's book Walther Pistols, From 1954 to 1985 all PPKs from serial 100,000 to 329,000-some were Manurhin made and Walther proofed. This fits with what other people say too. At some point they started finishing the pistols in Germany (Ulm is very close to the Manurhin factory) and eventually took over complete fabrication in the later 80's.
If all the eagles are the same (frame and slide) and there is no marking of year manufacture on the barrel shroud, then you have an early (50's) pistol. No serial number on the slide means it was never in military or police service, since it seems those agencies all insisted on every part, including the magazine, being stamped with the pistol's serial number.
7.65mm caliber marking means it was, like most PPK pistols, a .32 when it started out. To convert it from prohibited (caliber and barrel length) to restricted (longer barrel and new caliber) it was obviously rebarreled with some additional work done (headspace opened a bit and probably the slide's barrel port opened up a bit to accept the thicker .380 barrel). The ejector also needed to be ground down, or changed out, to let the bigger .380 go by. That's the part that sits to the left of the magazine well (looking down with the pistol pointed away from you) and also serves to lock back the slide on empty.
The pre-war and wartime .380 PPK used bottom magazine releases, since the recoil would jolt the magazine loose. If that happens to you, you can get a stronger magazine release spring, or there may already be one. For some reason, Walther PPs and PPKs recoil much more than most .380s. There's a guy on watherforums.com doing a study as to why.
The magazines for post-war PP and PPK in .380 are ribbed on the left side, where a small extra magazine follower part contacts the ejector / slide stop. If your magazines aren't ribbed, the ejector has been hand fitted to allow the .380 bullets by, but to still contact the magazine follower on empty and lock open the slide. That means, if it ever breaks, the replacement needs to be fitted again. Not a big deal, but careful work. Also, don't buy modern "380" magazines for this pistol, since they won't fit. You need the .32 magazines, which, again, hold .380 just fine.
So 50's gun, commercial, in nice condition. It looks like you have the original wrap-around 50's grips, before they split them at the back. Zehr Kool, ja!
Fake Can... 
