I think this is a Čezeta scooter from the former Czechoslovakia. It was made between 1957 and 1964 by the ČZ company (Česká Zbrojovka Strakonice).
They had two-stroke engines of 175 or 200 cc, and there were two models, 501 and 502, but the differences were mechanical, and I'm not sure you can tell them apart - well, I certainly couldn't.
These were regarded by some to be dangerous, in that the fuel tank is in the front, just behind the headlamp, and vulnerable in a collision, but I'm not sure that it's any worse than sitting over the fuel tank, as you do in a Lambretta.