From the National Archives, this is a small blown-up portion of a photo of the crowd from the day of the Gettysburg Address on Thursday, 19 November, 1863.
From the Archives Prologue Magazine site:
“In 1952, the chief of the Still Photo section at the National Archives, Josephine Cobb, discovered a glass plate negative taken by Mathew Brady of the speaker’s stand at Gettysburg on the day of its dedication as a National Cemetery.
Cobb estimated that the photo was taken around noontime[...]about three hours before Lincoln delivered his famous address.”
The original photo of the whole crowd is here. It’s amazing Cobb found him; I’ve been looking and I can’t see where he is!
Source: [National Archives: Prologue Magazine]