Early microwave oven safety
As far as leakage is concerned, the early household Amana/Raytheon Radaranges are very safe. The Amana units with the very thick door (typical of late 1960s, 70's and forward) were incredibly effective at stopping RF leakage. That superb door seal system is hard to economically duplicate today.
The units to be concerned about would be microwave ovens made prior to the early/mid 1970s or units with any sort of door or cavity damage. Also be careful of off-brand microwaves from the late 1960's and very early 1970's. Even so, just have the leakage checked with a legitimate, certification leakage tester (Holaday, Narda, Leader brand checkers).
And check for leakage out the air vents. If the magnetron wasn't installed correctly, you can find leakage in the strangest places.
... and FORGET about that stupid cell-phone microwave-oven leakage test that the doofuses are spreading on the internet. Totally invalid.