Chances are you'll get more by selling it.
It's probably either a bloody had print wall tile, a bloody foot print floor tile, a chalk outline, marble pedistol or some kind of barrel.
HOLY CRUD I HAVE ONE OF THOSE TOO.
I have it now, wondering, SHOULD I OPEN IT?! SHOULD I OPEN IT?!
AGGGGGGGGGGGGGGGGGGGGGGGGGH!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!