Some random thoughts.
The machine may have been built as much as 10 years before your
school obtained it, judging from the design.
This machine sounds like a transistorized version of the Monrobot,
which we of the list have recently become priviledged to know more about.
This machine may have been referred to as a Calculator and not a Computer.
There is mention of a "General Precision LGP-21" out there on the
web that approximates the design of your machine,
and it is circa 1963.
Good luck, I hope you find it.
John A.