Mark
I don't know exactly what makes this particular lure work but it does. I think it's a combo of all the design, the cupped eyes the placement of the lip under the chin, the line tie placement. Just a well planned out design.
These lures were manufactured in the 50's. Heddon tried to knock them off with a version that was identical except for a rounded lip instead of the squared off lip that they used. The Heddon version just doesn't catch fish like the original. The Millsite Deep Creep is one of the best designed lures that I have ever fished, it hunts like a starving coyote and it won't blow out until it reaches crazy speeds above 10 mph