Energy Consumption of Refrigerators
Being that this model is a SxS (Plus a third door), you will be looking at an energy hog ESPECIALLY with a Frost-Free system fitted to the unit. However, if this machine is big enough to fit all your goods (I assume you wish to purchase it?), then it may even save energy compared to running a half-full (or empty) refrigerator plus your full 'other' refrigerator (or more, if you have it).
I should also note that even today, the French Door and SxS models still consume ridiculous amounts of energy in the home, so you really are much better off with an Upside-Down model or conventional refrigerator of ANY age than this "thing."
However, I would debate the energy consumption of the Cyclic-Defrost Refrigerator models of the past. Those are not energy hogs by any means. I have heard of people using a "Kill-A-Watt" meter and measured older machines using less energy than current models.
Depending on the compressor Frigidaire used for these particular machines, I might be concerned about the reliability of the refrigerator in the long term, but I guess its come this far, so why not farther?
The biggest issue will be finding parts (Timer, Heating Element, Wiring Harness etc) for the automatic defrost system if it exists on this unit and IF it should break down at some point. This is why I would suggest a manual-defrost model if possible, since any available parts will be NOS and expensive.
I can't give a very accurate age on the unit, but considering its design and lack of sick-inducing colours, I would hint at late 70's or early 80's.