Thank you all for the input.
I'm being told that this is an 18th Century Swedish Sterling piece which predates the institution of Swedish silver dating system, which was begun in 1759. I believe they are claiming that because of another mark which I believe is a Swedish Import mark for .830 silver which wasn't used until 1912. I can post better pictures of the Swedish mark later.
The Simon Rosenau mark seems very clear, which means it can't be 18th Century Swedish Sterling.
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