I found this on the Old Ten Speed Gallery:
Katakura Silk was a Japanese bicycle manufacturer in the 50’s, 60’s, 70’s and 80’s. The company, once Japan’s largest manufacturer of Silk, began producing bicycles at a factory near Yokota that had produced aircraft parts during the war. The Japanese road cycling team at the 1964 Tokyo Olympics rode Katakura Silk. The brand was also well respected in Japanese Keirin racing.
This particular machine was manufactured at the height of the 70’s Bike Boom. A former factory employee told me this model was called the “PX” and made primarily for the U.S. market. Many were sold at the PX stores on U.S. military bases. Frame geometry is similar to sportif/randonneur type bicycles popular at the time.