It is an LTV Scout D first stage with strap-ons and a nose cone. The Scout D is a four stage satellite launcher made up of four different off the shelf motors. The fins are totally Scout and the small transition to a slightly larger diameter of the body just above the fins and just below the upper end of the stage makes it a "D". I'd post pictures I have except they are on a hard drive I have to find.
There aren't a lot of good Scout D pictures out there, but I've included the only one I have handy of a model I built back in the last century.
Scout Family on Wikipedia: https://en.wikipedia.org/wiki/Scout_(rocket_family) Note: There is a glitch when you click on this link. The trailing parentheses gets left off. On the page you get there is a lightbulb icon and beside it is the question "Did you mean: Scout (rocket family)?" Scout (rocket family) is a hot link so lick on that and it will take you where you want to go.
When you mentioned SA-4, I too thought it was something Ganef because had I researched that missile and drawn a plan of it to build back in my model rocket days. I didn't look closely enough at the picture until Mark mentioned saw tooth fins and when I looked closer and saw the fin tips and enlargement of the booster, it clicked as a LTV Scout D.
Looking at the picture, they must have wanted something that would lift a big payload fast but not too high. Most Scouts had several stages and this thing seems to be a single stage with strap on kickers to pop it off the pad. It might also be possible that they were exploring the addition of strap-ons to the Scout D to increase its thrust off the pad and the nose cone is a placeholder so they could focus on the interaction of the strap-ons with the booster and later add on the upper stages.
My search for LTV Scout info ended in 2000 with the building of my model. Mike Dorffler, who took the picture, was the designer of the smaller Scout model and provided me with a lot of Scout data that had come from LTV manuals that he had used to design the model kit for Estes. The material he gave me was only about Scouts that were actually built. If you want to see a pristine Scout D, go to the NASM on the Mall and head for the rocket gallery. It is the tallest thing there reaching from the bottom floor almost to the ceiling. My interest in building a D didn't happen until many years after my last NASM visit and I had a friend in the area go by and get my detail pictures.