Your best chance for narrowing it down within a few months is to find the manufacturing date codes on the pots, large chassis-mounted capacitors, or the power transformer. For example, your pots may have a manufacturing code something like "137-7407" which would indicate they were made by CTS (137) in the 7th week of 1974.
That's awesome! Of course, that's the only thing I didn't take a picture of! Thank you!!