Thank you all very much for the help. I went through the London makers’ mark list, and found about 4 candidates (John Harvey, James Morrison, John Payne, Thomas Whipham). Admittedly I have not yet compared against the Grimwade book.
However, looking online at Simon Jouet marks, it seems like he is the best candidate so far.
In particular, I notice the following similarities between the mark on this tray and his mark on a candlestick of his from another website.
Distinctive “in” and “out” marks on the side.
Notch at the top of the mark.
Curve in the visible portion of the J.
Thanks again for your interest and help.