Watch List notes:

SICILY. Syracuse. Dionysios I, 405-367 BC. Drachm (Bronze, 29 mm, 32.70 g, 8 h), possibly signed by an unidentified engraver, K.... ΣYPA Head of Athena to left, wearing Corinthian helmet decorated with a laurel wreath. Rev. 8 rayed sea-star between two dolphins swimming upwards; in field to left, below dolphin's dorsal fin, tiny letter K. Calciati 62 var. HGC 2, 1436 var. SNG ANS 455-469 var. (but none known with the Κ on the reverse). An apparently unknown and unpublished variety with the letter in the reverse field. Clear, with a noble head of Athena, and with an attractive brown patina. Good very fine.
From the PR Collection.

This coin is a rather startling novum that was, as usual, acquired because of its general attractiveness rather than for the highly unexpected letter on the reverse, which was, of course, then unnoticed! The question is, what is this Κ doing in the reverse field? The fact that the letter is very small immediately suggests that it is an engraver's signature, rather than that of a magistrate or other mint official, whose initial or symbol would have been much larger. The possibility that other examples with Κ exist, but have never been noticed, is a reasonable one. In any case, this is yet another case when a well-known series produces an unexpected surprise!.