1. A keris consists of two main parts, which are: 1) the blade (including the pesi); and 2) the ganja. The blade (including the pesi) represents a liṅga, whereas the ganja represents a yonī. Based on ancient Hindu beliefs, in traditional Javanese phylosophy, too, the unity of liṅga and yonī, symbolizes the hope for fertility, immortality (or continuation) and (both worldly and spiritual) power.
2. The blade of the keris always leans slightly over the ganja, which means that the blade is never entirely straight. This corresponds with the traditional Indonesian attitude, which implies that all people, regardless of their social status, ought to maintain a modest and respectful attitude at any given time. Not merely towards God, but also among each other.
3. The length of the blade of the keris usually is anywhere between 33 cm to 38 cm. Though some kerises from outside of Java can sometimes be up to 58 cm long. The smallest keris, however, is the Keris Buda made by the female empu Nyi Sombro in the Pajajaran era. This particular keris is approximately 16-18 cm long. Yet there are also many other tiny kerises, some only being 12 cm long, or yet even less than that. However, these tiny objects do not fall under the category of keris, rather do they get classified as amulets or talismans.
4. A genuine keris is forged by using at least two or three types of metal: 1) iron; 2) steel and 3) pamor. However, old kerises, such as ‘Keris Buda’, do not contain any steel. Kerises made from gold, zinc, or other types of metal, do not fall under the category of keris. Likewise, kerises which are not forged but (iron) casted, are also not considered kerises, but rather keris-like.
Though there are, of course, several other factors that can be used to classify a keris, yet the four points mentioned above are by far the most important criteria.
Reference: Harsrinuksmo, B., 2004: ‘Ensiklopedi Keris’. Jakarta: PT Gramedia Pustaka Utama. p. 9.