This consists of an image that forms part of the paper or polymer from the time of its manufacture and can be seen on both sides of the banknote, looking in detail, with different tones.

In particular, banknotes belonging to the F type have a watermark, except for the commemorative 100-peso banknote. The watermark on the commemorative 200-peso banknote is an image of the winged Victory. The watermark on the rest of the type F banknotes is an image of the bust-head figure of the banknote.

In addition, the 100-, 200-, commemorative 200-, 500-, and 1000-peso banknotes have another watermark which is the image of the denomination number.

Watermark on the 1000-peso banknote

Examination against the light

To observe this security feature, the banknote must be hold against the light.