1966 Petrus

[JWE]

Recently I was offered 6 bottles of '66 Petrus (from an estate) at 400 usd each. All 6 appeared to be in good condition but when standing them up the cork from one of the bottles had slipped in and was floating freely in the bottle. How does a cork get "sucked in" like this? The foil was the only thing keeping the wine from spilling onto the floor. Because of this I didn't buy, the other 5 are still for sale. No leakage, the level was very low in the neck just above the shouolders.