Once again you have proven your keen observation. Especially when one considers the 1717 farthing above is supposed to be a "dump" (or smaller) farthing. Here's a real 1717 dump farthing below for comparison (note the break of the legend on the obverse and the placement of leaf on the reverse) : "The death of Queen Anne thwarted attempts to issue her farthing, but the need for a copper coinage was no less after the accession of King George I (1714–1727). The price of copper had risen, so the new farthings were lighter than the previous issue, at 4.5–5.3 grams. The farthings struck in 1717 looked slightly odd as they were smaller, and thicker than the previous issues, with a diameter of 20–21 millimetres, and they are known as dump farthings. Farthings of 1719–1724 are slightly larger, at 22–23 millimetres, but are of the same weight" Other opinions appreciated, guy
I only caught it because I've made similar errors myself. When working through a large group of coins and a single piece like this presents itself, it's an easy mistake to make. Try giving a call to NGC. They should correct an error like this gratis.