Features 2 biplanes flying among the clouds on the front and a 3rd biplane flying among clouds and under a rainbow on the back.
Though no marking are present, due to its style I strongly suspect this mug was manufactured by Otagiri.
Copy 1: This mug has no chips, cracks, scratches, stains or crazing.
Copy 2: This mug has no chips, cracks, scratches, stains or crazing. There is wear present on the bottom rim, please see the last photo. Inside this mug there are a few imperfections from the manufacturing process, please have a look at the 5th photo.