In the later archaic period the coins come in as an important source of evidence.[2104] None of the inscribed ones appear to be earlier than the sixth century, the oldest being perhaps the electrum stater usually attributed to Halikarnassos, with the name of Phanes(?). The only characteristic letter (the alphabet belonging to the Ionic group) is the sign [heta] in place of Η to denote _eta_, which has not been found on any vase with the Ionic alphabet, and therefore betokens a very early date. Next comes an Attic stater of about 560 B.C., with the legend [(Α)☉Ε], which may be fitly compared with the oldest Panathenaic amphora,[2105] on which the dotted [☉] is also found. The earliest coins of Haliartos in Boeotia have the curious form 15[8]curious asper for the _spiritus asper_ or Η, dating apparently before 550 B.C.; the succession can thence be traced through 14[10]asper2 14[9]asper3 and [heta], down to about 480 B.C., when it is dropped entirely. At Himera in Sicily [heta] occurs in the fifth century for the _spiritus asper_, and is followed by the HH form, which in the West is employed down to about 400 B.C. On the early coins of Poseidonia (Paestum) the [M] form of Σ is found (550–480 B.C.), being also characteristic of Corinthian vases of the sixth century; it also lingers on in Crete, but in Sicily and elsewhere the [Σ] form of Attic and other alphabets is more usual, until replaced in the fifth century by Σ. Of the specially Ionic letters, Η (= _eta_) is found generally at an early date, as at Teos (540–400 B.C.), and also Ω. At Corinth the _koppa_ Ϙ for Κ is in use from the earliest times down to the days of the Achaean League, and does not therefore afford evidence of date by itself, but only of a local peculiarity, being equally universal on vases. The digamma is only found on coins of Elis and Crete, whereas it often occurs on early Greek vases.[2106] It may also be of interest to note that the [heta] form for the rough breathing occurs on the helmet of Hiero in the British Museum,[2107] which can be dated 480–470 B.C., and that the use of Η for _eta_ and of the four-lined [Σ] at Athens previous to the archonship of Eukleides can be deduced from the well-known fragment of Euripides[2108] in which the letters forming the name [ΘΗΣΕΥΣ] are carefully described. In the following pages illustrations of the points above noted will be fully detailed where occurring on the vases. The annexed scheme of alphabets used on vases (Fig. 173) will serve to give a general idea of the variations of form in different fabrics.