It is what's known as an "evasion" - a counterfeit coin made with legends that were close to, but not identical to, the legends on genuine coins. At the time they were in circulation, they were known as "Brummagems", because they were widely known to have been manufactured by button-and-badge-makers in the city of Birmingham.
The theory being that someone who was in a hurry (or who was illiterate) would see a pattern of letters that was "close enough" to a genuine coin, and accept it as genuine. And, if the counterfeiter was caught, he might escape a hanging if he could persuade the judge that his "medals" were sufficiently different from the coin of the realm, and it wasn't his fault if people got confused and spent them as money.
In this case, the name that's supposed to be around the king's head (if it were a genuine halfpenny) is "GEORGIVS III REX", not "GLORIOVS III VIS". Meanwhile, on the reverse, we see "BRITISH TARS" instead of "BRITANNIA". "Tar", in this instance, is the slang word for "sailor". So, it's ostensibly a "medal" in praise of British naval superiority. It's similarity to a British halfpenny is purely coincidental.

This piece is listed in the Atkins catalogue of evasions (and the Galata catalogue which uses Atkins numbers) as number 271, valued at 20 pounds in Fine (unfortunately, this one's condition is far worse than British Fine). Examples of this coin in better condition show a date "1771" below Britannia, but dates on evasions are usually fictitious; it was more likely to have been struck in the 1790s or early 1800s.
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