Help wanted!

I've seen several versions of those master cylinders myself. The power ones usually have a larger diameter piston than the manual cylinders. Most of those early cars have a retainer that holds the piston in the cylinder. It also holds the dust boot on one end. On the power cylinders there is usually just a little finger that bolts to one hole in the cylinder and extends over far enough to keep the piston in. Since they mount to a booster, they don't need a dust boot.