From: Elementary ep. 5.8
Event: Mr. Holder delivers a Beryl Coronet to Joan, to be delivered to Sherlock as a payment or memento of sorts from an earlier case.
Reference: From the adventure of the same name, we have a Mr. Holder and a mysterious Beryl Coronet. The circumstances of the canon piece are rather different than its appearance in this episode, but I and I’m sure all Sherlockians knew exactly what would be in the box when we saw Holder’s name. When Joan Watson commented on it being a crown, I have no doubt that all of us shouted at our TV screens: “It’s the Beryl Coronet!!”