The cover on this soap shows the 5th avenue address, dating it between 1938-1941. Because the factory imprint is still clearly visible on the soap, and there are no signs of use anywhere, I am convinced this is 100% NOS.
Like most of the soaps from “back in the day”, Seaforth pucks are tallow based lather bombs. The original Heather and Fern fragrance has, for the most part, “left the building”, but the fresh soapy scent is still quite present.