On pg. 26 I mention that Etruscan abecedaria have a sign shaped like a four-paned window in the spot typically reserved for ξ, i.e. between ν and ο. Until recently this sign was only known from Etruscan, or possibly Etruscan contexts, but the publication of a fragmentary abecedarium from Eretria shows that the sign in this shape and position was known in Euboea, and therefore is not a specifically Etruscan creation, but was simply taken over from the donor alphabet.
See Wachter, R. 2005. Annex zu Fragment 3 der Graffiti von Eretria. ZPE 151:84–6.