Gorgeous coin, Nikki. Genuine and valuable.
DO NOT CLEAN YOUR COIN. CLEANING RUINS VALUE.
27 grams is the right weight.
8 reales (8R). Guanajuato mint (Go). FR assayer initials.
The one in my picture is similar to yours. It sold to a collector for $200 US dollars during a 2020 auction. A coin dealer might offer $100 plus or minus $20 to buy it from you. The one in my picture is encapsulated and graded by NGC at AU58. Yours looks to be AU also.
Your coin carries a common date and mint mark. For better dates and mint marks, see this page:
The Mexico City (Mo) mint is pretty common. The one in my picture sold for $52 US dollars. The "bandaid" look on your coin lowers value substantially.
You did a good job getting the goo off the 8 reales. We always say "Don't clean a coin" because most people smear coins with silver polish and thus destroy them. In fact, there are professional coin cleaning services which do excellent jobs of making dirty coins look nice. Instead of "cleaning," it's called "conservation." Conservation is generally done by museum curators.