It looks like a genuine Maytag. I don't think that they were selling disposers made by others back then, not that there was anything wrong with a high end Instinkerator. My Maytag batch feed dates from 1992. When I moved into Greenbelt in 1981, I REALLY missed having a disposer; funny, it is a largely hidden, utilitarian appliance, but I really missed having one until I got the batch feed ISE.
There has never been nor does it look like there will ever be a disposal as amazing as Maytag. I prefer the batch feed with the reversing stopper. Its much easier to use than my new ISE.
We had an FC-5, purchased in 1990 for $29 as I presume NOS/NIB in the clearance room of an appliance dealer. It was harvest gold and the housing was shaped like the one in the picture below. It stayed behind when we sold our other place. If the subject disposer is a true Maytag, don't delay -- go after it. Best disposer I've ever had.