It doesn't seem to be a coin. Looks to me like it came off of someone's clothes. Like a button or something of the sort.
Looks like a key fob, may be very old and rare but not valuable at all. May have even been a key at one time. Better luck next time!
The tree looks like the old Wye Oak tree that was in Maryland. A few years ago the tree was blown over by a hurricane. A shame as it was well over 500 years old at the time. If it is the Wye Oak, it could be a souvenir.