Hello everybody, my first post on this fascinating forum. I'm very new to collecting so everything I read here is a learning experience. Anyways, saw this thread and thought I should add something to the discussion:
Swastikas painted on the walls and roof of a home in Bhutan - notice similarity with the design on the Japanese sword. I asked the house-lady and she told me the design, like many things in Bhutan, is Tibetan in origin. I know this thread is about swastikas on swords, but am posting these images below because of their similarity with the Japanese sword design.
Now, to keep the post fully relevant, check out this gubor (pommel) of an old Bhutanese patang that has been in my wife's family for several generations. This is the backside of the gubor, the front-side has pierced work more usually seen. In the background you can see more swastikas painted on the edges of the house's door area.
You will find swastikas in various designs all over the Himalayas, Tibet and South Asia as ancient Hindu and Buddhist religious symbols. Hope you find this interesting.