Almost certainly the widow of John Willis - see
viewtopic.php?f=74&t=23777
Mary Willis entered a mark as bucklemaker at 81, Bishopsgate Street on 26th June 1798.
11th January 1804 - The Proceedings of the Old Bailey Ref: t18040111-12 Extract only
“MARY WILLIS sworn. - On the 14th of December, the prisoner brought two spoons to my shop, which is a silversmith's “
Mary Willis appears to have been active for at least ten years as a pair of her buckles have been seen marked with "N" for 1808/9 (although her MW appears to be an overstrike - she probably bought them in and acted as a retailer ). Probably one of the few widows to continue her business for any length of time - Hester Bateman excepted.
NOTE
Will of John Willis of Saint Gregory by Saint Pauls , City of London proved at PCC 04 May 1798 does not relate. This John Willis had a wife and daughter called Elizabeth ! No mention of a Mary. £3.50 wasted!