The head of Athena is too large for the Hekte size coinage which may lend support to speculation that the die used was also used on a higher denomination. Liselotte Weidauer, in her book "Problems of early Electrum Coinage" (1975, Office du livre, Fribourg), describes how a number of the series of early coinage, including those of the Milesian and Phokaian standards, used the same dies within each of those series on a number of denominations. There are other Mytilene electrum coins on this website that also give cause for such speculation - see Coin #11259 and #11287.