It's a coin of Roman emperor Aurelian, struck in Alexandria, Egypt. The denomination is called a tetradrachm but it's not like a Greek tetradrachm, which is silver. This metal is a very low silver content bronze alloy. The full attribution of your coin is: EGYPT, Alexandria. Aurelian Regnal year 5 (CE 273/4) potin tetradrachm Obverse: AKΛΔOMAVPHΛIANOCCEB; draped cuirassed bust right Reverse: eagle standing left, head right, wings open, wreath in beak; ETOVC - E Reference: Emmett 3924.5, rarity of R1 (most common, in his rating scheme) Some notes: The date is on the reverse. ETOVC means something like "year of reign" and the year, stated as a letter, is on the right side of your coin. For this emperor and this reverse, that letter is going to be either an E, an S, or a Z. Of those choices, yours looks most like an E. Plus, according to Emmett, this reverse was only issued in his 5th year of reign so visible or not, that's by far the most likely date. The obverse description might vary slightly from what I've written. Emmett's book isn't big on noting minor differences in the legends. In case you are interested, here is what that legend means (it's a bunch of abbreviated names and titles): AVT[OKPATΩP] K[AICAP] Λ[OVKIOC] Δ[OMITIOC] AVPHΛIANOC CEB[ACTOC] = Imperator Caesar Lucius Domitius Aurelianus Augustus It is a collectible coin, not of high value. Many people (including me ) love coins of Roman Egypt. Here are a couple of comparisons currently for sale in "retail" online venues: https://www.vcoins.com/en/stores/ma...ia_198_tetradrachm__eagle/822507/Default.aspx The dealer is asking $50. https://www.vcoins.com/en/stores/zu...dria_choice_aef_273274_ce/575240/Default.aspx The dealer is asking $95.
