Seconded. I've worked with PCBs of that vintage quite a bit- both recently and closer to their era. They are absurdly heavy and fragile by modern standards, a

Seconded. I've worked with PCBs of that vintage quite a bit- both recently and closer to their era. They are absurdly heavy and fragile by modern standards, and were very prone to having the traces lift off the boards, to the point of being notorious for sudden electrical shorts. If memory serves, that problem persisted at least through the 1980s. I'm sure there was a technological development of PCBs that eased the issue; somebody who knows more on that subject may be able to clarify.