[size=18=12]χ
I think in classical Greek chi is pronounced as a an aspirated k. I’m certainly not an expert on Italian and English phonology, but this distinction (unaspirated-aspirated) seems to be the explanation for the difference between casa and case.
Later (but I don’t exactly know when) the chi turned into a fricative (just as the theta).
Ptolemaios
well, I’m no more expert of italian(or german) phonology than you are. ;D I’m just quoting from movies(from various countries) i saw before. lol. I looked more closely and in Smyth 26 the change of phonetic values through the time was explained.(Why by Zeus did I miss it before???) It suggestes that phi, chi, theta became spirants after about 300 AD.
and in the meantime there was the intermediate sounds like [size=18=12]πφ