the model year is encoded on the vin code. The 10th digit is the code, 1980 model year is A. I,O,Q are not used. So, your 1990 vehicle should have a L in the 10th digit. The date of manufacture is printed on the sticker on the left door below the latch. BMW looks for parts based on the serial number part of the vin. The aftermarket will look for when a vin split occured and then list their parts by date of manufacture. It is a good idea to always provide DoM as well as model year when ordering parts through the aftermarket.