From Lineagoe Book, National Society of the Daughters of the American Revolution - Volume 16:

Seth Mann (1724-1815) turned out from Braintree at the Lexington Alarm in Capt. Seth Turner's company. His oldest son, Seth, also served in the Revolution.

Seth Mann (1724-1815) served on the Lexington Alarm as a private in Capt. Seth Turner's company, Col. Benjamin Lincoln's regiment. He was born in Scituate; died in Braintree, Norfolk, Mass.

Grave says 91 so he may have been born in 1723.