Recently there have been a few offerings of Milt's drawings at Heritage Auctions. While other animation art items saw record prices, these pieces went for relatively modest dollar amounts.
The Mickey Mouse sketch looks like it was drawn in the late 1940s or 50s. To my knowledge Milt animated Mickey only one time for the short Mickey's Circus. And that was his debut as an animator in 1936.
That hand is too large.
When Milt drew characters for fans, he mostly sketched them in black and white. This is a rare color piece. It was drawn sometime during the 1950s. The style and line work is more graphic here than in his earlier production drawings for Bambi. Thumper has a resemblance to the rabbits from Sleeping Beauty.
The three Witches of Morva for The Black Cauldron. He recycles graphic character traits from his earlier animated personalities. But the top draughtsmanship is still there.
More on Milt's character designs for The Black Cauldron here: