There are many cacheted envelopes that are, as of yet, unknown actually used. Unknown, as used herein, means unknown to the author and editors.
Lone Scout [Magazine] "Application for Agency" Post Card
8/01/23
Chicago, IL
Printed
Black on manila 3¼" x 5½" card.
W.D. Boyce Co.
Also see the W.D. Boyce section, and see 17-2 in Additions, 1910s section.
Milwaukee Boy Scouts of America Stationery
Circa 1925
Milwaukee, WI
Printed
Black on blue U432 stamped envelope.
See 25-1 in Print Catalog.
Editors note: This is strictly conjecture, but it appears that, in pen & ink, the sender neatly spelled the first name of the addressee incorrectly - "Hairy" instead of "Harry" - , caught his mistake and rather than cross it out or throw it out, simply set it aside.
