The ESP Guitar Company

i got an offer for a viper-400, but i'm a little confused, since the viper changed a little over the past years. some vipers have white headstocks and a dual emg 81 configuration then there are ones with black headstocks and 2x81 again. and the newest model with black nickel hardware instead of regular black am i missing a model? the question actually is: which is the oldest model? because the guy i'm buying it from bought it in used condition as well. the thing i'm not getting is, that it seems to have a black headstock, black nickel hardware and 2x81. at least that's what it looks like on the pictures. i asked for more.