This stamp, honoring the Irish-born American sculptor
Augustus Saint-Gaudens (1848 – 1907), is part of the 1940 Famous Americans Issue.
Nice stamp with a great coin collecting theme!

As you mentioned, Saint-Gaudens is well known among coin collectors as the designer of the $20 "Saint-Gaudens" gold double eagle and the $10 "Indian Head" gold eagle, both minted from 1907 until 1933.