Sounds like your lights were converted. I know when we brought cars in the lights all had to be modified or exchanged. Sometimes it was to add a necessary light (as in side markers), sometimes it was just to get the DOT cert. Windows are the same thing. The standard is AS2 and AS1. Most MBs came with the proper glass though. Only the cheap versions weren't right.
Bosch Master, ASE Master, L1
33 years MB technician