Hunted a house that dates back to the 1700's today. Found a three wheat pocket spill (1944, 1944 & 1936), two modern pennies and the Valley Forge PA 1777-78 item. THought it was a whistle until I found the small metal item inside it. working on ID'ing it now.
My guess is that it's a commemorative trinket ? Does Valley Forge have a gift shop ? Possibly from 1977-78 to commemorate a past battle ? That's where I'd start to look. That thing is in too good a shape to be nearly 250 years old.