First up, an original, graphite, 1930 model sheet purchased from the estate of Les Clark:

Next, another original graphite Les Clark model sheet, this time of Mickey as the Sorcerer's Apprentice. Over the years, Dennis became good friends with Bob Jones, who worked closely with Joe Grant in the Disney Model Department from its inception. Dennis interviewed Jones extensively. Here's what Jones said about this next model sheet:
"Serious work on the Sorcerer's Apprentice had already been started when the Character Model Department got off the ground. However, the Sorcerer unit in another department had specialists doing the same work. They used a general purpose stamp - rather than the specialized one used solely in the Character Model Department. Since Les Clark was one of the authorities on Mickey Mouse, and was one of the head animators in this unit, his pencil initials would be required on the sheet before distribution."
Clark's "L.C." initials are visible in the lower right corner of the ink stamp. Here's the model sheet:

Finally, we have a change in artists for this last model sheet. This next one was executed by legendary newspaper strip artist Floyd Gottfredson, who titled the work, "Mickey Mouse Expressions and regular cast of characters." This huge piece was done in india ink and is signed by Gottfredson in the lower left corner. Dennis says this original was one of two Gottfredson created for the comics. Here it is:

Click this link to see more of my Dennis' outstanding collection.