Is old anchor hocking microwave cookware safe to use?

Microwave ovens can work for decades. They can fail for a variety of reasons related to malfunctions in the electronics, but they are generally pretty tough. But that doesn't mean they can be roughed up. Avoid slamming the door. Don't use metal inside unless the manufacturer's directions permit it. Cover all items that can possibly splatter. Keep the cavity clean. Food thrown around the cavity can continue to cook even if it's stuck to the inside, and, though the cavity is steel, the door most likely isn't. The door and the window are vulnerable to damage from shock (slamming the door) and from heated food that can melt portions of the assembly. The door shuts to press against the front of the cavity and form a microwave seal by virtue of the spacing. If damaged by stress or heat, there might be a problem. Microwave leakage is undesirable for exactly the reason you think it is. Direct any questions or doubts at a local appliance person. Phone calls are pretty cheap if not actually free. That's within the budget of most people.