Otis 7300 was an Otis door operator. There is also a DC conversion version (7300A, AC-DC converter to power DC motor). It is unknown exactly when this door operator was used, but it was used in the 1970s. Otis 7770A and 7770R door operators look similar, but have the motor in a box.
Old 1970s Otis Door Operator and elevator shaft "stuff"!
Otis 7300 door operator in action