Here you go, attached is the scene with a material and a gif showing the switch on and off.
- material created before GGX was introduced
- changed (Legacy mode set to OFF) in daily build '2015-06-20 1.1 legacy hotfix' and saved
- now opened in daily build '2015-07-22', where it opens with Legacy set to ON
Nevermind the question about the script, found it.