It is indeed the turn indicators. It's official name is Fixlight after the Fix factory where it was made but every one know them as 'takgök' (roof cuckoo) and was only available for two years between 1950-1952. It disappeared because it was to hard to see if it was indicating left or right in the dark, despite the blue center light and since it was inconvenient to mount a roof rack. It was also forbidden on most export markets.
I have never seen one with this bulky body though. I have one that I got from my uncle on my thirtieth birthday




https://sv.wikipedia.org/wiki/Fixlight