You are looking for pictures of the rotor head, the areas just below the head itself is called the swash-plate (2 parts), and below that is the Main Rotor Gear Box. (MRGB).
OH-6A are equal to Hughes 369 and MD500C models, 4 main rotor blades, the D and E models have the 5 bladed version. Would imagine that the MH-6 and newer versions have the later 5 bladed systems, with 4 bladed tail rotors like the Apache.