Lot 3279 in last week's Kelleher auction (sale 781) was in the "Ephemera" section of the catalog and was described as:
"The New-York Gazette: or The Weekly Post-Boy, No. 794, April 10, 1758; a remarkably well-preserved 4-page news paper with much of the content relating to the ongoing French and Indian War with a red handstamped Postal(?) marking on the front page; Very Fine. A very rare intact eighteenth century U.S. Colonial newspaper."
The "red handstamped Postal (?)" marking is is the 1/2p New York Colonial tax stamp used from 1757 to 1760. Scott Catalogue number RM9 catalogue value (2020) $1,600.