Rich asked "Are true hybrids (between 2 different species) sterile?"
The answer to that is usually they are either sterile or have significantly reduced fertility, but that is not always necessarily the case. Interspecific hybrids can be fertile (many of them are in plants, orchids for example) and I expect that some butterfly hybrids are fertile too. Just off the top of my head, Papilio appalachiensis arose from natural hybridisation between two species, and of course the offspring of the original parents must have been fertile otherwise the new species wouldn't have arisen from them.
Well, that certainly qualifies as a legitimate wild caught example of miokensis. A reasonably descent example but, what might have caused the localized dis-coloration on the wings (near the bases of the hind wings) ? Water stain ? A seldom seen item with a stiff asking price given the fact that it's hard to overlook that stain. Too expensive to experiment on "fixing" the unsightly problem. I guess I generally appreciate the item for the natural rarity that it is however, I'd have to pass given the price and somewhat unsightly condition. Just my opinion.
That photo looks more like miokensis for sure, however urvilleanus on New Ireland can look like this, price seems reasonable if it is true miokensis, The Paris auction house had one listed last year with an estimate of around 7,500 euro ( don't know if it sold though ). There is one on eBay today, which, if I had the money I certainly would pay the £1,200 asking price and it's not even A-, but it's from Edward (Ted) Archer, a fine collector I had the honour of taking to about Ornithoptera many years ago, the seller also has a very reasonably priced pair of allotei (£1,500) which I would add to the basket.