Hello Masha ::: I am pretty sure you have a silver decadrachm from Ptolemaic Egypt. The woman on the front is Arsinoe II Philadelphus, who lived around 275BC. Her name, APΣINOHΣ ΦIΛA�'EΛΦOY, appears in Greek letters on the back of the coin, along with two cornucopias.
The silver coin in our picture is an amazing specimen from Heritage Auctions (ha.com). You can easily make out the patterns and inscriptions. This is not true with your coin, which has much more wear and much less appeal. The Heritage coin sold for $13000 US dollars during a 2014 auction. Your coin would probably sell for $100 to a collector of ancient coins.
The same pattern is found on gold coins of the time. The gold coin pictured above comes from Stacks Bowers Ponterio. It sold for $20000.
Here is the detailed description of the silver coin from the Heritage auction:
PTOLEMAIC EGYPT. Arsinoe II Philadelphus (277-270 BC). AR decadrachm (32mm, 35.59 gm, 12h). Posthumous issue of Alexandria under Ptolemy II, ca. 253-246 BC. Veiled head of the deified Arsinoe right, wearing stephane and horn of Ammon, lotus-tipped scepter in background, it's tip visible abover head, ΩΩ in left field / APΣINOHΣ ΦIΛA�'EΛΦOY, double cornucopiae, grape bunches hanging at sides, bound with fillet. Svoronos 959. Troxell, Museum Notes 28 (1983), p. 35, 55g. Very rare, particularly so with these mintmarks. Light graffito N in reverse field, otherwise deeply struck and beautifully toned. NGC Choice XF★ 5/5 - 4/5. From The Lexington Collection of Jonathan K. Kern.The ostentatious display of Egypt's wealth under the Ptolemies was not confined to gold coinage. Ptolemy I and his immediate successors also struck silver coins in larger denominations than any contemporary kingdom or city-state. Along with the vast outpouring of gold in the name of his sister-wife Arsinoe II, Ptolemy II also struck silver decadrachms displaying her veiled portrait backed with the cornucopia, symbolizing Egypt's agricultural abundance. Having died in about 270 BC, Arsinoe is shown as a goddess, with the tip of a ram's horn (symbolic of the god Ammon) poking out from beneath her veil, and the lotus-tipped scepter of the goddess Isis just visible above her head.