You will probably never know. The 4560 was widely cloned and many small companies from the 70's are gone. There was a cabinet maker on every block in the 70's.

Very common was to clone the 4560 and install an EVM 15. The 4560 has little resale value, ditto EVM's. That was the cheapest set of the type, and was widely sold.

If JBL loaded, the JBL's will be worth more than the boxes.

4560 is loud but starts rolling at a higher frequency than the A7. Subs would be a must IMHO.