Looks like a pendant. Makes me think of Ireland/Celtic time. Just noting down what I feel about the coin, not know.
It could be a half Real or 8 Real (piece of eight), if we knew what it weighed and it's diameter we could ID it better.
Based upon the overall position of the design elements from what I can infer from the images, I believe it is likely a 1R or 2R.
It is very worn but compared to your photo of the 1745 I can make out the small shield with the three crosses inside the large shield. I can also make out the lion to the upper right of the small shield. The letters VTRA match and the unusual design of the 5 in the date match. I has seen discussions of counterfeits, is it worth checking per it's value? Maybe since it is well worn it was real? BTW, it weights 5.4 grams. Thanks for your help everybody.
Doug never ceases to amaze me....... There are some other guys and gals here that are extremely knowledeable (that I hold in high regard), but I don't think Doug ever sleeps or takes his eyes off the computer screen....
Those aren't crosses, they're fleur de lis - flowers. In that condition the coin isn't worth more than a few dollars. And I have no reason to suspect it is fake.