Can't help you with your date query, sernas88. (Someone else should chime in.) But if I may: how about that? This National RV-490 even has its own quartet of batteries of the same brand. No need back in the ‘80s to head over to a RadioShack location to buy "C" cells to start recording sounds (such as vocals of conversations). Looks pristine, too, Asian alphabet documentation and all, except perhaps that irregular pattern on the LL SELECT key(?)
Does this unit have a circular VU meter? Didn't another brand like Sony use round VUs in some of its high-end, "Professional"-strength Pressman models (costing maybe $699) in the 1990s?
I hope that the AC power cord required for a smaller (and likely originally much cheaper) Panasonic that I found yesterday on eBay is the same type as the one for yours: an oval plug (IEC C1) that fits into the unit end of the connection. I don't yet have a crop of AC power cords to "trial and error" my way into finding the cord with the right fit.
Uh, did you find this on eBay? Is it going back in a listing on that website -- with a starting bid of ...?