There is a $5,000.00 limit...
I have sometimes used an arbitrary value of $500 for this type of thing -- because, in my mind, it is high enough that a loss/theft will get investigated and low enough that it is not worth a new employee risking their job over. But that's just me and the To: and From: lines are always generic -- not "Joe's Loose Diamonds and Gems."
We have (well, had) an excellent B&M jeweler and my sibs used to send me things to take to this shop to get repaired/re-sized.