U.S. Dues Stamps Not Valid for Postage
in the Philippines

1914 SEPTEMBER 16: MANILA to CHICAGO
Franked with 2c U.S. issue, subjected to 2c upon arrival.

The 2c Dues is proper as the total dues is 4 Philippine centavos which
is equivalent to 2 U.S. cents. I am sure that the auxilliary marking
"U.S. STAMPS NOT VALID FOR POSTAGE" was applied in the Philippines.
which is a seldomly seen marking.