[Dave at Pelican Parts]

Have you checked the tech article on ignition timing here? It has pictures of a couple of different fans, and the markings on those fans.

Usually a red line is the timing mark, and a '0' is TDC. The TDC mark is not always present. The position of the marks versus the fan blades is pretty consistent, so if your mark is next to the fan blade shown in the pictures of the article it is most likely correct.

--DD