WOW! That must have been one of Amana's budget models for 1983. In 1984, I purchased a top of the line Amana, all electronic buttons, clock. Going back to the 1970's, my mother had an Amana Radar range that had a timber knob dial and power setting knob. Amana in those days was the last word in Microwave ovens. As for cancer; microwave ovens NOT put out ionizing radiation like an X-ray machine. It is just high frequency RF that can cause burns if you were exposed to the magnetron and for any microwave, always best not to stand directly in front of it while in operation, old or new.
What you say about other appliances is true, but this boleshit. I have used vintage microwaves, and never had an issue. They have electromagnetic radiation, but it does not expose people to it. That is a myth. These older microwaves were better!
Old microwaves like the Amana Radar Range were built like a tank, with high quality components and yes, little if any of the microwave energy that is non-ionizing will get past the door seals. The screen in the window are smaller than the microwaves themselves. If in good operation, an old microwave will work just fine, maybe not as powerful, lack a rotating platter. The Amana's have a stirrer that scatters the microwaves for more even cooking. Generally, they are safe as long as the unit is not damaged and or old capacitors etc that may not work well over time, cracked insulation and that sort of thing.