How safe is a 1969 zinsco electrical panel?

They are not at all safe and are junk that needs to be recycled and never installed even in a barn let alone a home. Zinsco company went out of business partly because it was discovered that their breakers did not trip when they were supposed to. For this reason they are nothing but a fire hazard and are not to be trusted to protect the wiring in your home or your family from a fire. Do not use any Zinsco or FPE service panel. Destroy this panel so that no one can ever use it.