This is the Float Switch Base Lock Nut, part number WPW10195038.  This item came from a  Kenmore Model 665.12783K311 Dishwasher, Maytag Dishwasher Model MDB8959SBW3 or KitchenAid Dishwasher Model KUDS301XBL4, but it will fit other models and brands where the part number matches.  Some wear and residue from normal use, but fully functional.  Price includes shipping, USPS First Class.