The McKinley Birthplace Museum just received a donation of this envelope. It has the “Post office Dedication Niles, Ohio Birthplace Wm. McKinley 25th President 1843 1901” postmark, which was the official postmark used the day the post office in Niles opened. This would be the new (for 1933) post office that is still in use today. The date is postmarked as “Niles, Ohio Jan 1, 1933 8AM.” I just love the calligraphic handwriting on the address, too.