The first of the Pro 4 range were the Pro 4 (https://www.ebay.co.uk/i/17433286654...yABEgKXxPD_BwE). The second version (and presumably improved) were the Pro 4A (with one 'A'). The third version were the Pro 4AA (with two 'A's), and the fourth and final version were the Pro 4AAA (with three 'A's). Since they are a development of the Pro 4AAs, one would assume they have an improved comfort and performance.

I cannot imagine Koss continuing to manufacture previous Pro 4 designs, once they were superseded by a later version.

My Pro 4AAs look exactly like yours, with a sage-green finish and a solid and inflexible head band. Those shown in the ebay link have a different, and IMO preferable, colour, which might have been a later colour change by Koss. They look to be NOS (the seller appears to be a trader who buys up old stock, and the one he has for sale is his last), and not copies.