Big E wrote:
> Any help with date and what it was worn on would be greatly appreciated.
It was worn on the uniform of a US Army soldier. The emblem on your button is the Great Seal of the United States. So, these buttons are called "Great Seal" buttons.
Mackaydon has already told you the date-range for the manufacturer stated on your button's backmark, "Am[erican] Button Co. Newark New Jersey", 1901-1920.
Getting more specific than 1901-1920:
The US Army adopted the Great Seal button for general service in 1902. The first version of it did not have a raised rim around its edge. The raised-rim version began to be produced "about" 1910 (I can't remember the exact date). The American Button Company's factory burned in 1917, although the company officially remained in business until it was bought by the Waterbury Button Company in 1920. So, your button dates from approximately 1910 to no later than 1917.