Philippine Special Delivery

HI Everybody,
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. ***

lets see if it works this time

https://www.hipstamp.com/listing/ph...AqJ8EALw_wcB
Found another good comparison: group of 6 stamps also with the serial number, without the OB print

Hi W1, and welcome to the forum. First of all, what you have is a "Plate Number Block of 4" - the number on the selvage is the number of the plate that was used to print these stamps. Your stamps have the Scott catalog # Philippines EO1. When you look up what they are worth make sure they are the correct item - both stamps you found are different.
The fist one you mention has "specimen" overprinted on it, the overprint makes it rare.
The second one ( on Hipstamp ) is an imperforated plate block with catalog number Philippines E6.

Peter

Thanks Peter, Im picking up one of those on ebay just a couple years out of print.

So I've gotten the Scotts Catalog and have been learning how to identify them. There are several panes of four which do not have perforations, and while I think I have the right Scott number Im not sure about identifying these as I dont see any notations about missing perforations. The Jose Rizal stamps in the link below appear to be 241 A40 2c. Does "Impt." stand for imperforate? (from googling Scotts abbreviations I could not establish that). Thanks for the advice!
https://drive.google.com/drive/u/0/...51oiL2c8E9l1