Lord Sailor:

In the old marking specification the N number wasn't on the side of the wing. It was painted once on the top, and again on the bottom. Haw.

Conventinally, it was on top of the right panel, and the bottom of the left, but the top marking could extend across both panels. THere were regulations concerning the height and width of the numbers, and they were painted (both top and bottom) to be viewed as upright when seen from the tail of the plane.

Bill.