I do believe the window is symbolic of Mr. Jones, his psychological well-being. He will not disclose the least meaning of most of his work. He prefers the ideas come alive in the mind of the veiwer, and feels the interpretation lies solely in the eyes of the beholder.
However...notice the profound clarity of the wheel, and especially of the plants below. The window is softly sketched, while they are carefully drawn with precision, as is most of his work. I happen to know at the time he was undergoing a health crisis. I've never asked him why the disparity in the objects in the drawing. I don't think he would tell. Ever true to his nature, he took one day off to rest.