A 3400 is basically an early layout 4000. There's nothing different or special about it apart from its rarity and the front bezel - which can't even accomodate a CD drive.
When Amazing Computing first reviewed the 4000, it was a black 3400 they used to show the internal features.
The metallic label on the back of my 4000 I even suspect says 3400 on it - the "4000" identifier is a mere sticker on top of it.
