What's this board game with an old radio and some country flags on it?
Must be a specific version of the Radio Broadcast Game:
https://boardgamegeek.com/boardgame/159448/radio-sende-spiel

While the images on boardgamegeek show slightly different boards, your board has the same features: namely exactly 100 spaces and old wartime flags for Germany and Italy. So the description fits perfectly and it must be some version of this game:

"This is a simple roll and move game with the objective of touring wartime Germany and being the first to reach the final (100) space.

However, the primary objective of the game was to encourage both patriotism and obedience to wartime rules, specifically the prohibition on listening to foreign broadcasters.

When landing on domestic transmitter spaces, the players must carry out certain actions: sing a ditty, send a message, make a weather report or sing a military song. But if they land on a foreign transmitter space, they must exclaim "I have committed a criminal offense", pay a pfennig into the pot and go back to start. Worst is if they land on London's transmitter, when they must shout "God punish England!" and pay 5 pfennig into the pot as well as start over. The pot is taken by the winner."

Not sure where you found this but the game is likely quite old (like 50s or so), I'ld like to own a copy of that if you're selling :)