When Thing grabs Fester's nose, he is a left hand, instead of his usual right. A moment later, when Things shakes his finger at Fester, he is a right hand again.
The Addams' safe has a spinning tumbler but no actual locking mechanism (rods) as seen after Fester opens it.
Four and a half minutes in, after Thing throws the brush at Uncle Fester and shakes a finger at him, the actor attached to Thing's hand can partially be seen briefly beyond the edge of the table.