Early Mk 4 would have had the tall M1 exposed turrets, a mildot reticle, and blacked-out trim rings.
Different Vari-X III variations but generally low, capped, coin-adjust elevation and windage, and a duplex reticle.
Also used to be a blacked-out Vari-X III Tactical 4.5-14 with tall, capped target turrets, but can't remember definitively if there was a 3.5-10.