I have the opportunity to purchase this coin and am looking to see if it is authentic or if someone can tell where it is from. i ave done some research on the subject and know it is a Spanish reale of the shield type. see pics below. the info i have on it: 4.5 grams and approx 22.5 mm in diameter. it appears to have an I and an R on either side of the shield. i have not been able to figure out what mint it may be from or if it is a repro coin. no discernible date on either side that i can see. all i have are these two pictures. any help is greatly appreciated!