Crosby's City Post, 2c Carmine, 54L1, Large to Huge Margins, Tied by Company Oval Datestamp on Illustrated Advertising Cover

Lyon records only 7 stamped Crosby covers, 6 with the Underhill & Co. Corner advertisements.
The stamp with large to huge margins incl. sheet margin at bottom, with a scuff at the bottom left of the bottom margin. Used on a window ventilator manufacturer's illustrated advertising cover to local street address.