Yes, as Sam mentioned above, that was a casino modification to eliminate frequent calls for us to leave the slot shop and come down to the casino floor to free up jammed escalators when I worked in the casinos in the 60's!
Even though going down to the floor was a nice break, visit with the Keno runners and Cocktail Waitress', Etc.
, it was irritating to be pulled away from an intensive breakdown of a mech in the middle of the job!
Also the lower bar of which you speak is the holding bar as the advance bar is at the top!
Here is a jpg on the Mills escalator, kind of hard to read but if you increase the size of the image it is easier!
Ciao!
MONTI