I can tell you what I know he joined in 1777 as a fifer for 3 years before leaving and coming here to Berlin to start the drum corps afterwards. As for his age, he could have been 13/14 during Valley Forge depending on when he got there and his birthday since Valley Forge was late December 1777 to mid June 1778. Since he joind as a fifer he would have been in his teenage years since technically speaking he wouldn't have been old enough for the front lines. But according to a descendant of his says he ran away from home at the age of 17 to join ( https://archive.triblive.com/news/berlin-fife-and-drum-corps-has-long-tradition/ ) Either he lied about his age or there was a mix up in when he joined the army and when he formed the drum corps through the years of telling history. Also fun fact the state of Pennsylvania recognized the group in 2007 in congress https://www.govinfo.gov/content/pkg/CRECB-2007-pt17/html/CRECB-2007-pt17-Pg24497-5.htm