Found minecart with chest in abandon mineshaft. When the item is picked up, it breaks into a minecart and a chest. However when the item is placed in an inventory or in as picture frame (it has no chest), and when the cursor points at it the label "minecart with chest" is displayed over it. No other items display their name. You can use the item to crasft a minecart with chest by adding a chest.... which sounds really odd...