Thanks everybody for your reactions, i learned alot from them. I'm from Holland, the province of Friesland, the same region where the batavus bikes are being made. Their factory isn't very far from where i live.
As for the serial numbers, i really can't find them, i've held the bicycle upside down and everything. I've done a little research myself. It seems that the serial numbers batavus used start with the number of the year they have been made in. My bikes serial number starts with an 1. The post of cuda2k indicates my bike would have been made between 78 and 82 so the build year would be 1981.
So the bike is a little bit older than me. I'm not going to change anything on the bike, it's going to stay as original as possible. I had to change the steeringtape and saddle pen in order to make it rideable for me, but if I could have left that original I would have.