Hey ts1... Flat buttons are a fairly common find in the water. Two/three piece buttons like Eagle buttons, less so because they are very light and float downstream more easily. I wish you luck in your spot, I've had fair to middling luck in and around Hagerstown creek sites. If you get the chance, come to The South Mountain Relic and Coin Club meeting in Williamsport. We meet every third Tuesday. We are on FaceBook.
Have you ever found a button in the water? I'm just curious. I have a site I'm getting ready to check out soon and it dates to late 1700's. Property has extensive creek frontage and its near an old bridge. By the way...I'm in Hagerstown.