British & English Copper Coin collecting

GEORGE I Farthing 1719 Last A in BRITANNIA over I G over G in GEORGIVS

Im amazed four different reverse dies were used this is something ive never encountered before anywhere, in fact there’s every chance of a 5th obverse type turning up at some point as a die must exist with the original v in Georgivs not over struck.

With four possibly five different dies in existence why the rarity of this 1719 A over I farthing ? very strange indeed. Farthing grades a problem free fine.