I sculpted 4 busts for Dragon many years ago. They were never a set, but came one to a box along with apprpopriate Dragon (DML) model airplane kits.
The busts were of Richthofen, Rickenbacker, Ernst Udet and an obscure German Navy pilot. The Udet bust is easy to distinguish from the other because his hat is identical to Richthofen's and he has a large turned up fur collar. The hat on the last figure has Naval insignia which looks quite different from the army hat.
Also, every single paint-job I have seen of Ernst Udet shows him with a leather flight suit. This is WRONG! The flight suit should be in brown cloth as it actually represents a captured French flying overall. This was duplicated from photos of Udet.
Hope this helps.