When did Porsche replase plastik wendow?

Answer 1

Assuming this question is in reference to the first-generation 911 Targa, Porsche offered the Targa with a glass rear window alongside the standard removal plastic item beginning in 1968.

If in reference to the Boxster, the troublesome plastic rear window was replaced by a glass item beginning in 2003, though this switch was accompanied by a decrease in the size of the window itself.