The sound was that of the unvoiced dental stop. The English t, however, is not dental but alveolar, being pronounced, as d also, not by putting the tongue against the teeth but against their sockets.
Kris felt the intent gazes of both of his deputies, who left the obvious unvoiced.
At the end of words the voiced sound is often written with -s, the unvoiced with -ss as in his and hiss.
The symbol G was a new coinage in the 3rd century B.C. The pronunciation of C throughout the period of classical Latin was that of an unvoiced guttural stop (k).
In medieval and modern Greek, however, this has become the unvoiced sound represented in English by th in thin, thick, pith.