The Japanese Post Office was state-of-the-art during World War I.
The era of air mail also began at this time. Before a regular airmail service could be started, it had a little experimentation.
Anyway, this first experimental flight from Tokyo to Osaka and back made a big fuss. It wasn't just postcards about this one memorable event that were printed and special cancellation issued, but the definitive stamps at 1½ sen (postage postcard domestic) and 3 sen (domestic letter) were specially made for the postal flight in a small edition (1½ sen: 50,000 pieces, 3 sen: 30,000 pieces)
issued with the silhouette of a biplane overprinted. The blue 1½ sen stamp was overprinted in red, the one on the red 3 sen stamp in indigo.
These overprint stamps went on sale on October 3rd and were exclusively for the franking of letters or cards of this mail flight; moreover, they lost their validity at the end of the month.
Genuine issues and special cancel
Genuine Features
1. Deep Indent
2. Eyelet (not easy to see on blue stamp with red ovpt.)
3. Eyelet
4. Tail rudder made up of 5 distict sections
5. Wide pilot seat area with white dot sometimes visible
6. Eyelet
7. Rounded precise corners
8. Visible wing struts
Fakes
No eyelets
Struts are dashes
Wing tip angles converge
Plane and wigs are crude
It sold on eBay for large amount
Wing tips angle wrong
Sold online for $800
Wing tip angles and plane color wrong
Wing frame too large and wrong color
Plane position very wrong
Wing tips eounded
Planes too steep angle and wrong position
Tail has only three instead of five elements
Plane positions wrung
Wing tip angles converge
Wing tip angles wrong
