Type 45 Colotti two speed transaxle. Made exclusively for the 1964 Brabham BT12 Indy car by Colotti GSD and installed in the John Zink Urschel Trackburner. After extensive research and correspondence with Marco Colotti, It's deemed possible they only made 1 or 2 of these boxes exclusively for Brabham. Cast with Colotti-Francis and G.S.D(Gear Speed Developments). A very, very rare and interesting piece of racing history.