The maker's mark IP with pellet between in oval most closely resembles the mark of John Plimmer, who is listed as a smallworker. A similar mark is also listed in Grimwade as no. 3670 in the unregistered marks with a doubtful attribution to John Parker II. Neither is likely to be the maker of these dishes, whereas Preedy, who is known to have made ambassadorial silver, seems a more likely candidate.
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