The outbreak of WWII in The New York Times — Poland — September 12 - 15, 1939 — Sold as a set Options:Include an archival box (Additional $45) we checked every one against

we checked every one against an authoritative source

An excellent write up on the event from the National History Education Clearinghouse answers  the question

as does the frame

including the date the cornerstone was laid

Also available for a limited time

The outbreak of WWII in The New York Times — Poland — September 12 - 15, 1939 — Sold as a set Options:Include an archival box (Additional $45) we checked every one againstThe New York Times for September 12 15, 1939 reporting the outbreak of World War II. September 12, 1939: POLES HALT ENEMY ON WIDE FRONT; FRENCH CONTINUE TO GAIN IN WEST; REICH TO INTENSIFY SHIPPING WAR September 13, 1939: NAZIS SAY WARSAW IS ENCIRCLED; POLES ASSERT FOE IS HURLED BACK; FRENCH DRIVE ON SAARBRUECKEN September 14, 1939: GERMAN BOMBING OPEN TOWNS; BRITAIN THREATENS TO RETALIATE; NAZI OFFENSIVE GAINS IN POLAND September 15, 1939: RUSSIA