That's a great coin.
It depicts the Spanish colonial domination of both Old and New World with the Latin inscription -- "VTRAQUE VNUM", meaning the union of two worlds--as shown. 34 mm and 13.54 grams. A few years ago all "4s" were more valuable than the "8s" and your coin was worth $110 in VG. Mexico City mint.
BTW, your coin has two royal crowns on the date side; another variety of the same coin, with about a 10% increase in value, has an imperial crown on the left and the royal crown on the right.
Don......