Prod. 2006 - Dumbo (II)
Directed (again) by Sam Armstrong, assistant directors Lloyd Richardson and W. Hays, layout Dick Kelsey.
This 2nd draft dated 5/7/41.
Animation of Casey Junior by John McManus, Frank Grundeen, Don Tobin, Cornett Wood, Don Patterson, John Reed and Poul Kossoff, regular effects by Jim Escalante (my guess), with characters by Claude Smith, Edwin Fourcher, Hugh Fraser (Elephants) and Howard Swift (Ringmaster).
We have seen most of the Casey Junior animators as effects animators on Pinocchio already: McManus, Grundeen, Escalante, Tobin, Wood and Kossoff are all found on the Pinocchio draft.
I bet John Reed was another of the people called Jack...