Original model sheets are difficult to find. However, model sheets offer an amazing view into the creative mind of the artist responsible for the character. Stat (early versions of the photocopy process) model sheets offer a great deal of appeal. Here are a few from Dumbo:
Stat Model Sheets
(click to enlarge)
----- DATABASE NOTES -----
From Dumbo (1941). A stat model sheet of Casey Jones, Jr. "Revised Casey Jones Jr." "-2006-" "1-2-41" Dimensions: 14w X 11h. Acquired 2000. SeqID-0496.