wonder why, the rotor sits up so high not like our 60s but funny none the less. 
Each blade has a droop stop on it to keep the blade from contacting the fwd fuselage when the blades are turning at a slow RPM. As they get to speed, centrifugal force lets the droop stops pop out and the blades are allow to go down farther. So the guy marshalling the helicopter watches these droops stops to make sure they come back in as the blades slow down. He gives a thumb in or out to let the pilot know the position of the stops. Even though they are spinning at the same RPM as the blade root, you can still see them. You can tell if even just one is stuck out.
I have no idea if the newer 53s have these, but the B and C models I crewed did.