ᛟᛟᛟᛟᛟᛟᛟᛟᛟᛟᛟᛟᛟᛟᛟᛟᛟᛟᛟᛟᛟᛟᛟᛟᛟᛟᛟᛟᛟᛟᛟᛟᛟᛟᛟᛟᛟᛟᛟᛟᛟᛟᛟᛟᛟOn pg. 27 I wrote "Since Etruscan did not have a contrast between /o/ and /u/ they eliminated the sign." This sentence needs some elaboration. First of all, archaic Etruscan alphabets do retain the letter as a dead letter. See Wallace 2008:17–18. Second, while it is true that there was no contrast between /o/ and /u/ in Etruscan it now seems pretty clear that the Etruscans did have a way of writing /o/. In addition to the well known case of the bilingual inscription from Pesaro which has the form frontac (Um 1.7, 1st BCE), there is now also a form cnovies in an 5th century BCE inscription for Civita Castellana (CIE II, 1, 5). The inscription reads cnovi{e}ies mi "I am of cnovie". Given its location the inscription is probably recording a Faliscan praenomen—hence the attempt to represent the "exophoneme" /o/—but mi and the genitive ending -es shows the text was Etruscan. The shape of the o in both these examples is like a vertical fish (see this image of the Pesaro bilingual here.) and this is precisely the shape that o has in the (indirectly) Etruscan-derived Runic alphabet as illustrated above.
See Maras, D. F. 2009. Note in margine al CIE II, 1, 5. Studi etruschi 74:237–47.