The denominations of the stamped paper and adhesive revenue stamps issued for use in the Philippines were expressed in terms of the monetary unit which was current at the time of their issue.  The monetary unit of Spain underwent numerous changes during the more than three hundred years of Spanish Dominion in the Philippines.  The currency of Spain circulated in the Philippines and the denomination of Philippine stamped paper and adhesive revenue stamps were at certain periods expressed in terms of Spanish currency. But the currency of Spanish America also circulated in the Philippines, This was originally due to the fact that for many years all  communication with Spain was by way of Mexico and almost all exports from the Philippines were shipped to Mexico, which sent Mexican silver to the Philippines in payment thereof.  Hence, the denominations of Philippine stamped paper and adhesive   revenue stamps were, during certain periods, expressed in terms of the current Spanish American currency. 

The several monetary units in terms of which the denominations of Philippine stamped paper and adhesive revenue stamps were expressed at ii various times were the following:

1 Real  ) = (20 cuartos)
1 Real de Plata ) = 2 medio reales = ( 4 cuartillos)  = 1/8 peso (Mex)
1 Real Fuerte )
1 Escudo ) = 100 centimos de escudo =  1/2 peso (Mex)
1 Peseta ) = 100 centimos de peseta =  1/5 peso (Mex)
1 Peso )
1 Peso FUERTE ) = 100 centimos = 1000 milesimas = 8 reales 
= 2 escudos
= 5 pesetas

For more than two hundred years subsequent to 1640 the REAL DE PLATA, also called REAL PUERTE or more often simply, REAL, was the principal monetary unit of both Spanish America and the Philippines.  The PESO eventually replaced the REAL as the   monetary unit of Spanish America, but in the beginning both the PESO and the REAL were in use.  For more than one hundred years subsequent to 1640, the account of receipts and expenditures of the  Philippine Government was kept in terms of PESOS, TOMINS, and GRANOS. One PESO was equal to 8 tomins.  Thus TOMIN was simply another name for REAL.  One TOMIN was equal to twelve GRANOS.  For possibly one hundred years prior to 1868, the account of receipts and expenditures of the Philippine Government was kept In terms of PESOS, REALES and CUARTOS.  One PESO was equal to 8 Reales and 1 REAL was equal to 20 Quartos.  A MEDIO REAL was one half Real.  A CUARTILLO or QUARTILLO was one fourth REAL.  The Denominations were  expressed in terms of the REAL:  On  Philippine stamped paper from 1640 until the end of 1867; on DERECHO JUDICIAL stamps of the Spanish Colonies (Including the Philippines) from 1856 to 1865; on Philippine Derecho Judicial stamps of 1878.

The Escudo was the official monetary unit of Spain from June 26, 1864, until October 18, 1868.  By the Royal Order of September 21, 1866, the Treasurer of the Philippines was advised that the Royal Order of March 21, 1865, should be complied within the Philippines. The Royal Order of March 21, 1865, is as follows:

Most Excellent Sir; It having been decreed by Royal Order of 8th of the current (month) that in all the Colonial dominions, and to count from 1st of July next coming, the ESCUDO must be the monetary unit when there may be necessary the expression of amounts in book-keeping and in all public documents, there must be adjusted to said unit the different kinds of stamps and stamped paper in use in the Colonial provinces. This change, however, cannot take place on the expressed date in these Islands with respect to said stamps and stamped paper because, in addition to this, that it would be impossible that the National Stamp Factory could print and remit them in such short time, it would produce damages of importance to have to make invalid many of the stamps and stamped paper now in use, as also the next to remit to these Islands for the biennial period of 1866-67, and the excessive expense which the precise surcharging of the same would occasion until the arrival of the new requisitions which would necessary to make the values adjusted to the monetary unit, ESCUDO.

In view of that explained, the Quean (Whom God Protect) has deigned to command that for that which pertains to those Islands, there should be continued the use of the stamps and stamped paper with the values which they express In PESOS and REALES FUERTES until end of  December of 1867, advising Your Lordship that in the future the calculation of the stamps and stamped paper necessary in those Islands should be for a biennial period, and the requisition should be made with the due anticipation, to the end that, before the period begins in which they must be used, they may be found at their destination.  Finally, I remit to Your Lordship a statement attached of the values which the different classes of stamps and stamped paper which may be consumed in those Islands from the 1st of January of 1868, must express, taking for pattern the monetary unit, ESCUDO.  By Royal Order I tell it to you for your   knowledge and  corresponding effects.  God guard you, etc. Madrid, 21 of March of 1865. Sir Superior Civil Governor of the Islands of Porto Rico and of Philippines. (Pages  176-177, Volume 13, Legislation Ultramarina [1868] by San Pedro).

In the Philippines, denominations were expressed in ESCUDOS on stamped paper from  January 1, 1868 to December 31, 1871; on Derechos de Firma stamps of 1868 (1867?) to 1870.

The PESETA became the monetary unit of Spain on October 19, 1868, and has remained the monetary unit of Spain ever since that date.  It has not been possible to find a decree requiring that the denominations of Philippine stamps and stamped paper be  expressed in terms of the PESETA.

The denominations actually were expressed in PESETAS:  however, on  stamped paper from January 1, 1872 to December 31, 1877; Philippine Derechos de Firma stamps of  1873- 75; on the Derecho Judicial stamp of 1874.