It is not clear that Greek took over ï¿½ with this value, for in one Theran inscription e a are found combined as equivalent to T - H, while the regular representation of ï¿½ and x f and K or 9 (koppa) 8 respectively.
The explanation is possible, but it is not easy to see why, for example, the symbol 9 or cp = Koppa, the Latin Q, should have been utilized for a sound so different as p-h; nor, again, why the symbol for 0 (e) by losing its cross stroke should become 4), seeing that the sounds of o and outside Aeolic (a dialect which is not here in question) are never confused.
It represents the Koppa of the earliest Greek alphabets surviving in that form of the Ionic alphabet, which ultimately superseded all others, merely as the numerical symbol for 90.
How would you define koppa? Add your definition here.