It's hard to say exactly what went on with your cz. Especially with not being able to make out the serial number and the marks on the frame. A better picture of the marks and a picture of the top of the slide would help. The markings below the ejection port are well forward of were the German proof marks usually were. It looks like the serial number is either 437,xxx or 477,xxx both of which should have had a slide that was marked FNH. Later slides should have had KAL 7,65 on the left side. Also you have the shortest slide serrations I've ever seen on a CZ-27 slide It's also a little unusual to have CZ marked grips instead of blank ones on these serial numbers although those are easy to swap out. Is the barrel marked in any way? My best guess is that your cz was put together or repaired shortly after the Germans lost Czechoslovakia, probably with a new slide stamped with the serial number to match your frame.