I looked around and it appears to be a Medieval Grosso of Arezzo in Tuscany. Some similar coins: http://numismaclub.com/unt/177144-silver_grosso_with_st_donatus_arezzo_republic_1250___1350_ad.html https://www.lamoneta.it/topic/66746-grosso-di-arezzo/ https://www.artemideaste.com/auction/view/433/525 https://www.deamoneta.com/auctions/view/507/100 It seems to be a relatively scarce coin, nice find!
It looks good to me. Despite the apparent lack of circulation wear, it does show signs of surface silver loss from burial conditions and nascent crystallization, which might not be ideal in terms of value but is good a diagnostic for authenticity.
