My first Dillon was a 450 bought new probably over 30 years ago. It did not have Tool Heads, and the Powder Measure and Priming System were both manually operated. Great press, but it needed a Star Wheel Bad. You rotated it using a shell in the press.
It was sold, and I upgraded to an early version of the 550. I owned it for a long time, then I got an opportunity to buy a later model version with a few upgrades dirt cheap. The original owner decided to get into 600 yard Bench Rest. He started ordering things he thought he would need for loading TWO Rifles without consulting with a REAL Bench Rest Shooter. He bought two 550's and started adding a few aftermarket improvements. Then he got with a REAL Bench Rest Shooter and learned that he really needed different Reloading Equipment to win with. He put his 550 up for sale, and my brother and I bought both of them. I then sold my old 550 to a buddy of mine.
A note on the priming system. I have Cleaned, and I have Polished, and Dry Lubed, and Aligned the Priming System multiple times. It will work great for a while, then start skipping picking up primers again when it gets a little dirty. What I have ended up doing is visually checking to make sure I have a primer picked up and facing up every time. If it starts skipping I will start pulling the slide all the way back by pulling on the vertical pin on the back with a finger to make sure that it comes all the way back, until I decide to tear it down and clean it again.
I would not trade my Dillon for any other press for loading handgun ammunition.
Bob R