6 additional pure were added in sale #2, and were used as part of a trade to buy a Stormy Festivizer. They wind up here (the other keys seen were not involved): https://backpack.tf/profiles/76561198119140602#!/compare/1496361600/1496448000

And regarding sale #4, how can you know exactly which sale was the effect you're trying to price? There were several sales from the 4th to the 6th, which is the gap in your compare link.