Greg,
The portable cleans itself very well, and for the most part is pretty low maintenance. I am not sure what its made out of, the lower part is a very thick plastic, the plug is grounded, and the motor is conpletely sealed.
Portable disposals were more common late in the 40's and through the 1950's. The James company had one that could even be converted to permanant! This GE is much newer, my guess based on the mechanism is sometime in the 1970's.
1976 ISE: When that thing squealed at me my heart broke! I've wondered at just calling ISE authorized service and seeing if they can rebuild it. Its the bearing under the disk, ISE uses a plastic shield on their better models to protect the drain chamber from corrosion. After 30 years of sitting idle, water got under the shield on this one and went right for the bearing. The motor still turns, but is very very tight!
I saw that Maytag made disposer on ebay, that was towards the end of their making them. As a kid I remember going to Polk Brothers(big furniture/appliance store chain in Chicago years ago) and they had a batch feed model on display that ran. Their demo was to toss in a few roofing nails and let the maytag chew them. I was always mesmerized when the salesman did that!