Our inch as in any inch it is also 4 quarters, if you carefully look at the picture of this gold curb chain you will see one side says in (inches) with 4 quarters and another side is mm (millimeters), so the 5 divisions you are referring to is for mm which are usually divided in 5mm each, and since 1 inch is approximately 25mm (25.4mm exactly) you see on one side of the ruler 4 quarters for an inch and on the other side 5 divisions by 5mm each.