OCJohn,
Lathe appears to be missing handle/knob from right hand QCGB selector and it's hard to tell whether end of the selector is damaged or not. Clausing might still have parts in stock. You now have access to Downloads and I presume have downloaded the manual, However, suggest that you also download the Atlas 3996 manual and parts list as it has been edited and cleaned up far more than the one that actually says 101.28910.
Phone number for Clausing Industrial is 800-323-0972 or 800-535-6553. If they no longer have a part in stock or on order, they will usually email you a scan or the original drawing, The drawings were all originally scanned to .TIF which I prefer as I have a .TIF editor and years of experience at using it. But few today know how to do that so they will usually also convert drawings to .PDF. If a drawing is not already in Downloads, I request that you forward it to me for clean-up and eventual upload. Their drawings were all scanned several decades ago and no attempt was made to clean any of them up!