Well, you sure have a lot of us taking strolls down Memory Lane!
Back when, the safest bow that you could put in the hands of a young'n was an all-fiberglass model. It was quite bombproof, almost kidproof, and did the job day in and day out. They got dropped and dry-fired, dug into dirt and dens, and a wipe-off got them shooting again.
The question, if I read it aright, was how safe are those old warhorses to shoot today? My own Bear Green Fox is safe as can be, I lend it to kids just starting to shoot, and it has never been used when not in my sight. But one from a yard sale or an auction? Because I don't know the history, I would check it out thoroughly. Look for gouges and lifted splinters of glass, like any other bow.
A section of nylon hose will reveal such like if passed over the surfaces of the bow. Once found, see if they are in a critical, working section of the bow. No? Go shoot. Yes?
Well, I am not learned enough in the ins and outs of bow repair, so I would ask my questions to the people who do that. Could be that a little injection of 420 LokTite will fix it. If not, then the bow will likely need deep-sixing to a wall or hallowed burial, with honors to its years of devoted service to adult and child alike.
Used to be, all kids except the very rich started with these once they came out. Before that, it was a lemonwood or homemade bow. I have a definite soft spot for these bows, they are rough and ready playmates, trusted with the safety of our children. I hope yours passes the tests.
Killdeer