Grimwade records two William Sumners.  William Sumner I was apprenticed to Thomas Chawner, making him part of the Chawner company.  His first mark was entered in partnership with Richard Crossley, in 1775.  He entered his first mark on his own on 6^th April 1782 as a plate-worker.  He entered several other marks, including marks as a spoon-maker, up to 1803.  He is believed to have died by 18^th March 1807 when his wife Mary entered her first mark.