Details & changes.

Through out the years, there has been many types of lenses. These are just some examples.

These are Hella lenses. The one on the left is the oldest, I believe they were used on the 1950 and 1951 models, but I'm not sure .
These are Bosch lenses. The left one with both VW and Bosch logo, the right one with only Bosch logo.