This is one of the cases Sonny used to carry his harmonicas around when he travelled.  When Sonny was touring, they didn’t have the fancy cases that we have today with individual slots for each harmonica.  These are essentially camera cases and Sonny would pile his harps up inside them.  This case has a couple of stickers on it including a U.S. Customs sticker which is a clear indivation that Sonny travelled out of the country with it.