Puzzle of the (17th) Century

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At first glance, this object would appear to be a simple case of the Metropolitan Museum of Art commissioning another one of their E.P. reproduction pieces through Gorham Manufacturing. It is the known four-legged service tray created by Simeon Souman of New York circa 1735-1745. They're known and surface. But here there is an engraving on the bottom for a "Farewell Dinner" on "January 24 1980" for an organization shown as "S.P.S.I. 1684-1980". ["S.P.S.J." might be an alternative reading.] There is nothing to indicate that the dinner was held at the museum, so it may have been worked-up for another location. Three of these trays turned up still together. The only thing American that seems to related to the seventeenth century founding date might be the role of Quakers in the settlements surrounding Philadelphia...some were already there before William Penn came over, but real organizing begins around this time. Annual meetings established a few years before, became monthly in this year. And the first slave ship sailed into those waters at that time...something the Friends were forming opposition too. The engraving seems to indicate the end of some long lived society rather than a goodbye to a member, but that's not clear at this point. Anyone got a clue what this might be?

Set 1: The tray...

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Set 2: The engravings...

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Set 3: A related MMA/ Gorham E.P. reproduction creamer for Benjamin Burt Boston circa 1765 found near the tray and possibly from this same source, though without special engravings....there was a milk stain on the lip, so it had been used at least once..