I would like to answer my own question, as I have investigated and found some interesting facts. The vendor name for the **Fort steel frames** since the **year 2008** is **Intec**. Search for **Intec** , and you will find all the old frames. In this forum thread user _verreweg_ explains the differences since the _renaming_ (the manufacturer’s name is still **Fort** ): The new frames are _cavity sealed_ , have a chemical pre-treatment with phosphates ( _phosphated_) and new stickers with the Intec label.