In the middle of 1975 VW changed the geometry of the convertible rear window. The later windows were introduced at chassis number: 1552012218. This or higher and you have a mid75 and later window.
The convertible rear window frame is made of steel with an attached tacking form all around.
We urge the convertible restorer to read the restoration tip below concerning the convertible rear windows.
If the steel frame is in perfect condition you can purchase, and attach a new plastic tacking form. However, we strongly recommend that you consider the complete rear window frame with the wood already attached to its metal frame, as a unit ready to apply to the new top.
Any rear window frame and glass may be installed in any new top, regardless of year!