It looks like it was made in that time frame too.

Copyright and trademark are two different things. Only copyright expires

Here’s a summary of what you can and cannot do to mickey: https://web.law.duke.edu/cspd/mickey/

TL;DR: you can use the mickey character in derivative works (copyright), but you cant use the character in a way that makes people think the work is made by disney (trademark)

public domain :)