Unknown maker mark on Silver Plated Spirit Kettle

This is one piece of a set that I bought from an auction in New England, U.S. The set has a hugh tray, spirit kettle, tea and coffee pots, sugar, creamer, spooner. The tray alone weighsover 13 lbs. The set came from a family estate. All the pieces I believe to be silverplate, all are marked with this mark on the bottom. I looked in the Encyclopedia of American Silver Manufactures, by D T Rainwater and some of the English Hallmarks but have not found anything. Please! Who is the maker, is it silverplate, how old is it?Is this enough information, do you need more photos?
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