This description appears to contain an inconsistency, as 8 Reales coins from Mexico, especially from 1813, are typically struck in silver, not copper. If you have a copper coin labeled as an 8 Reales from Oaxaca, it might be a pattern, token, or a very unusual piece. Assuming it’s a genuine 1813 Mexico Oaxaca 8 Reales, it would be an incredibly rare and valuable silver coin from the early 19th century, during a turbulent period in Mexican history, just before or during the Mexican War of Independence. If it truly is a copper piece, it could be a contemporary token or a private issue, which would still make it quite rare and interesting, especially if it mimics the design of official coinage. For a precise assessment, I recommend having it examined by a reputable numismatist or coin grading service to confirm its authenticity, composition, and historical significance. Such a piece, whether silver or copper, holds great collectible potential due to its rarity and historical context.