Spitfire Cockpit Question

In the October edition of “Todays Pilot” there is a great article about Training in a TR9 G-CCCA in Dutch markings. On page 34 there are cockpit photographs showing the main panel and each side of the cockpit similar to the style of the Pilots Notes. There is a GPs where the Gun Sight would have been located but I was surprised to see that Frame 8 is hidden by a small shelf like attachment and the K Gas is in the main panel. Is this arrangement particular to the TR9? I dont recall seing this before in MKV or LF16s.