The box resembles an old W bin cabinet that someone converted into what appears (the photos are very dark) to be a double eighteen reflex cabinet. The drivers should date back to the late 1970’s to early 1980’s when 200 watts was considered a lot of power.
If the cabinet is still solid, you could replace the drivers and, re-tune the cabinet to achieve optimum performance for whatever woofers you are eyeing. Only you can determine if the upgrade, or buying possibly a used JBL 728 would be a better investment.
Best Regards,