Voltar v2, Iron Grenadier General, was released as part of the 2012 Operation Bear Trap G.I.Joe Convention Exclusive Box Set.
The only real collector's issue in obtaining Voltar v2 is that the Convention Set was made in limited quantities. Note that Voltar's helmet is a soft plastic and does not fit his head very well. For instance, it's difficult to get the eyepiece over his eye, without cocking the helmet somewhat forward and down.
Oktober Guard is the correct spelling for this set, but it is commonly erroneously listed as October Guard.