Checking around EBay, I found the following listing for the Marx Pack Mule.
http://www.ebay.com/itm/MARX-HORSE-PACK-MULE-WITH-ACCESSORIES-/321642451541?pt=Vintage_Antique_Toys_US&hash=item4ae3625255
This is an interesting combinations of pieces. The vendor added the Stuart packs and harness to the mule. To complete the set he added the Stuart mounted pioneer with hat and saddle to the Marx horse from the farm set. The set is at $19.87 with four days and ten hours to go.
This party also has the Mattel Derringer gun belt buckle listed at $49.99 no bids.
interesting comb!!