Many of the coins have the OGH 3.1 slab during which you generally did NOT have loose grading standards. I've also seen some Wells Fargo coins with CAC stickers, and John Albanese tends to be pretty tough grading Saints.
Don't forget, over 50% of the hoard (12,000 coins) were MS-65 or below....there the market got oversupplied and you couldn't really cut prices at those grades because they already traded as generic common bullion. That's why dealers got fed up with Wells Fargo NM's. They were already a generic common even before the hoard and in the MS65 grades or below plentiful enough. Then you had thousands more in each grade.
No wonder they got indigestion.
I find it strange that Gillio hasn't revealed more details. It's not like it's top secret or he did something illegal. Common sense would indicate either he had a sensitive lead at a bank that had the coins OR they came from some individual or institution where someone maybe cut some corners. Maybe a private citizen from Central or South America had the coins and a family member or government official decided to liquidate it and take his/her cut secretly.
I doubt they came from Europe since the American dealers had experts scouring those banks in the 1960's and 1970's. This would be a record hoard in size, hard to believe it lasted until the mid-1990's. Possible, but highly unlikely.
A small or midsized South American, Central American, or Mexican bank....some leader of a military junta....a south of the border government agency that aquired the coins. Those are some possibilities.
The coins were probably on the books for about $400,000, the face value of the coins. Gold was about $375/oz. so the coins were worth just under $7.5 million based on bullion value. Most of the coins initially sold for just over $1,100 retail so assuming that Gillio bought them all as 1 group (not segmenting the coins by quality) for about half of that (a nice markup above the spot price of $375/oz.)....he probably paid about $10-$11 MM.