Thank all for your comments and advice.
I did have asbestos tests made of both the dust and fragments left from the sealant from the side windows, and in both tests they could not find any asbestos.
However, I also took a sample from the similar sealant putty used on the rear window, and here they unfortunately found asbestos fibres!!
The sealant putty on the rear window feels much more brittle and could in many places along the window be peeled off with a finger, whereas it had to be grinded off on the side windows. I therefore believe a different sealant has been used. The sealant on the side windows seems more like the putty used everywhere else in the hardtop for the crome trim, which I believe is strip chalk.
But what is left is that even though I have only partially removed the sealant on the rear window (with my fingers) I unfortunately cleaned it up afterwards with a normal vacuum cleaner without a special filter to capture the asbestos fibres, as I had no idea about the asbestos at that time, and they may now have ended up everywhere in our house! 😢
I will now have additional dust tests made in the house to find out how bad it is.
Another thing that popped up during my research is PCB, which was often used between 1950-1980 in flexible sealants for windows in houses. This material is now banned world wide because it is also toxic and can cause cancer! The question is now, if PCB was also used in sealant putty for our hard tops for the w113!? 😕
Happy New Year!