My dad's 30-ish year old Seiko has white crud at the 12:00 marker.  I think it is adhesive from an old repair (possibly a crystal repair with the dial still in the case?).  Any thoughts?  Would it be difficult to remove?  I'd like to clean it off, but as a newbie I also want to leave well enough alone.  I have cleaned the case and band ultra-sonically and have installed a new crystal, crown and cover gasket along with a new battery.   I'm tempted to put it back together as is and give it back