[capttb]

As Faster mentioned Capacity Plates are only required on powered vessels less than a certain length (26 ft. ???). Catalina mounts a small metal "Builders Plaque" on the outside companionway threshold that has model and hull numbers and states "This vessel conforms to ABYC standards" Blah, blah, blah. This is closest thing I can think of to a "certificate of compliance" plaque. Other builders place them inside companionway and other places.
Now, I really can't remember if Cals (or any boats) in the 70's had such plaques, but I'm doubtful.