Vintage Monroe Model LA7-200 Adding Machine Calculator w/ Power Cord (Untested)

Description

Vintage Monroe Model LA7-200 Adding Machine Calculator with Power Cord.
Powers up when plugged in, makes sounds but I do not know how to use it.
Overall condition is poor, with Monroe lettering missing on two of the three sides. The adding machine is dirty, but no visible dents, deep scratches or cracks in any part of the metal. The + key as a crack on it horizontally, and the cable is fraying a little.
This item should be considered for parts or repair, or if cleaned up a display piece only.