Hello and welcome.

As for what you have, we've got good news and bad news for you.
The good news is, we can identify it for you. We've seen them here on the forum numerous times before, usually posted by someone who's just as confused about them as you are; the old thread you linked to was just the first of many.
Here's one that was posted last year, with a link to another older one.
The bad news is, it's not a genuine coin. I was correct with my hypothesis way back then - it's a brass replica of a Spanish colonial "cob". Given how common this particular replica seems to be, I assume it was mass-produced for sale or giveaway at or with something pirate-themed. Given you found this one metal detecting, I suspect someone was having a "pirate treasure hunt game" and this one was never found.
As was noted in the other threads, the design on this one is much cruder than on your typical replica cob. The "owl face" that the crown has morphed into is particularly distinctive. It's possible that whoever made it was copying off a drawing or picture of a coin, rather than an actual coin.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis