Labrys is a doubleheaded axe, known to the Classical Greeks as a pelekus or sagaris, and to the Romans as a bipennis.
From Historia Nummorum:
The double-axe, pelekusπελεκυς, was the well-known badge of Tenedos, but its significance was much disputed in antiquity (see Maonald, Coin Types, p. 68, and B. M. C., Troas, p. xlvi f.). Aristotle 's explanation (ap. Steph. Byz. s. v. Τενεδος) of the Tenedian coin-types as representing the axe with which a royal law-giver of Tenedos punished adulterers— and his own son—is not now likely to find acceptance. (On Professor Ridgeway 's view that the axe on the coins is the representative of a primitive barter-currency of axes conjectured by him to have existed at Tenedos, see B. M. C., Troas, p. xlvii note.) It will he noticed that on the coins, from circ. B.C. 420, the double-axe is accompanied by a bunch of grapes as a constant symbol (once an amphora is attached by a fillet to the axe), a circumstance that suggests that at any rate from the fifth century B.C. the double-axe at Tenedos was regarded as an attribute or cultus-object of Dionysos who may have been worshipped as at Pherae in Thessaly (see supra, p. 308) as Dionysos PelekosΠελεκος (see Wroth, B. M. C., Troas, p. xlvii; N. C., 1897, p. 113 f.; cf. Rhein. Mus., 1897, p. 203; cf. also p. 406). A similar inference may be drawn from the coins on which the axe appears upon a basis. With regard to the janiform head of the obverse, it may be remarked that such heads are not peculiar to Tenedos (cf. Lampsacus, etc.), and their explanation is difficult. Here, perhaps, Zeus and Hera are intended, at any rate on the later coins (B. M. C., Troas, p. xlviii). On the Tenedian coin-types see also Babelon, Traité, p. 370 ff.