Thanks to all for the input. I later found a site dealing with paint schemes that also listed that as the reason.
If anyone knows of a good site listing Japanese aircraft markings with illustrations of Group, Squadron, and Flight insignias etc. I'd love to have it.
I'm trying to determine the time, place, ownership and other particulars for some of the aircraft I've posted on this site. There doesn't appear to be much, or as much, info on Japanese aircraft.
Thanks.