On November 16, 1992 the Philippines issued 5 postal tax stamps to aid those affected by the Mt. Pinatubo eruptions of June 1991. The following information is quoted from Philatelic Phillipine Philatelic Journal
, vol.XXX no.2, second quarter of 2008, page 6.
"As part of the nationwide campaign to aid the victims, in November 1992 Pres. Ramos issued Proclamations 64 and 64A that placed a surcharge on all types of mail (25c per domestic mail & 1 peso per international item) to operate from 16 November 1992 to 28 February 1993 - 105 days."
However, a businessman in Manila sued the government and the tax was only effective until Feb. 1, 1993.
Again, from the Phillipine Philatelic Journal
. "Subsequently, the stamps were reissued on June 14, 1993 and used for regular postage until exhausted."
Here is the 25s stamp. I don't have the four 1 peso stamps which are the same format and similar in design.