A2 Bulb

[golden_creature]

I have just purchased an A2 Aviator. Brilliant torch. (No pun intended). Can anyone tell me why the top third of the bulb appears frosted? Does this improve the performance in some way?
thanks
Golden_Creature

 

[Illum]

I think it has something to do with diffusing the hotspot...

I never really noticed it since its not the only lamp assembly that has a frosted head