In the closing credits, "Miscellaneons Crew" can be seen.
At 11:00 minutes in, Jack is working at the drawing table using a drafting arm designed for a right-handed person, where the control knob is held in the left hand and drawing is performed with the right. A lefty, especially one with Jack's OCD, would have the opposite left-handed arm on his drawing table (Jack is shown as a lefty as he draws and throws with his left hand).