This just in from Are Myklebust:

[On this website you will find what supposing is Walt Disney’s Ex Libris (or bookplate):

http://bookplatejunkie.blogspot.com/2006/09/cartoonists-wanted.html

Is it genuine?
And if so, when did he start to use it?

See also the Ex Libris belonging to Frieda and Remus Harris - the grandson of Joel Chandler Harris!]