Question about Franked Envelopes

Hi

Found this franked envelope in a boxed lot. It is postmarked London, Amsterdam, and New York. Studying the envelope I am unable to determine the sender. The back of the envelope has what appears to be a crown. Don't know if that is simply a feature of a particular brand of envelopes used back in 1863 or something more significant. The envelope is addressed to a Surgeon at Sing Sing prison in New York named George J. Fisher, in care of Bailliere Brothers in NY, a publishing firm. Did some research on Google and found George J. Fisher wrote a number of medical books during his life and I guess this particular piece of correspondence must have pertained to that aspect of his life.



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As I recall the monarchy in France was eliminated in the French revolution, and it was not just the king and queen who were killed by the revolutionaries. I would think that the raised design on the back was simply a pretty design, or at most a design being used by the company or institution where the sender worked.

Looks like a Ducal crown.. With a W on the left ? People who know about monogrammes can identify this house.