actually its not possible to destinguish an E-4 from an E-3 just looking at it!
the only difference was that the E-4 had MG-FF/M that were able to fire mineshells.
btw, if Maddox decides to make an E-3 as THE 109 in SoW:BoB it would be a mistake because the two main variants during this time were the E-1 (non 20mm canons) and the E-4! almost all so far produced E-3 were rearmed to be E-4s
