Posted by scvirginia (Charleston, SC - Zone 9a) on Jun 25, 2020 7:41 PM concerning plant:
Description from the 1933 catalog, Royal Iris Gardens (J. C. Nicholls, Jr., Camillus, NY), p.72:
GIGANTICOERULEA ALBA. 4–5 ft. The same as the type, but an exceedingly beautiful pure brilliant white. A gloriously beautiful Iris.