An oddity I found among some covers.

As best as I can tell, the engravings match the "Religious Freedom" theme and the stamp appears to be postmarked on the first day of issue.
The bottom line reads "Courtesy Haynes Trebor" and "The Salomons".
I came upon this reference to an article Haynes Trebor apparently wrote on the subject that year:
Quote:
Trebor, Haynes, ed. The Flushing Remonstrance (The Origin of Religious Freedom in America). Flushing: Bowne House Historical Society, 1957.
Not sure about the reference to "The Salomons" though.
Anyone care to elaborate?