User blog comment:Grayson Phillips/chapter 415/@comment-1906999-20100812023557

Actually, it looked like that is what he had in the flashback.. While it was never stated whether or not it was the Hogyoku, it does look a lot like it. It doesn't fit with our current timeline though. The flashback had to of happened before TBtP, because Gin had yet to join the Gotei 13. If Aizen had the Hogyoku before then, then that raises the question of how Urahara got it back from him and still hadn't suspected Aizen of anything. Then again, it might just end up being something completely different than what we think it is and be a major plot twist or something.