Um... Everyone is entitled to their opinions woodbeef, but for starters:
1) There is no such thing as an export model Yugo SKS. This applied only to the M48BO. This is not my opinion, it's the opinion of Branko Bogdonovich, the world expert on Yugo small arms and the official historian of the factory that made these rifles and of Joe Poyer who literally wrote the book on the SKS.
2) There is a HUGE difference between a 59/66 and a 59/66AB1. The former, only a few thousand made and unissued examples are stupid-rare. The latter made in the hundreds of thousands, less rare, but still VERY uncommon in unissued condition these days. I'm not clear which was offered to the original poster.
3) 53 Izzies are BY FAR more common than any 1949 SKS, regardless of refurb or franken pin. There are a total of ZERO non-refurb 1949 SKS's in North American than anyone has documented, so that's a moot point. There are dozens of '53 Izzies out there from the IZH import. I've personally held at least 6 of them.
4) Re the Marstar crate, them being consecutive means nothing. ALL the unissued Yugo SKS's marstar sold came in consecutive s/n crates. Of the crate in question, no two rifles went to the same person in the end as I recall.
5) I simply have to challenge you on your assertion you've been offered 4 of these rifles still in the grease. I frankly don't believe you - sorry. I would believe maybe one was in the grease, but without proof I don't believe 4. Degreased and lightly used is NOT the same thing as unissued still in the cosmo - just ask the guys who unwrapped their Irish Contract No.4 Enfields and then tried to sell them for what they paid

. In the last year there have been maybe two unissued in the grease yugo SKS's offered for sale here on the EE. I've been looking. One I bought, the other I sold
All that to say, you may only be willing to pay $450, but at least 10 guys two years ago bought unissued examples sight unseen for $500 (or $550?) plus shipping and they all sold in just a few days. None have been offered in any quantity since then. These were the more common 59/66AB1 models.
Hell, I think unissued Longbranches are only worth $400 but the EE here proves me wrong all the time.