In my grandfather's collection we have these four "Philippine Special Delivery" stamps. They are printed with "OB" (official business), and the backing has a serial number "113813" on it.
Any thoughts on how to value them as a lot, when as reference I've found this single stamp without the "O.B." listed at around $190? http://www.stampcircuit.com/stamp-A...james-bendon*** Moved by Staff to a more appropriate forum. ***