数の日本の自衛隊海軍旗 - Japanese Naval Flags for Numbers 0 to 9

Flag being represented by numbers is common property of modern navies.  Famously there is the International Maritime Code, but several nations have their own kinds of flags for numbers.  NATO has them, as does Russia, and so do the Japanese.

Here are the unique flags of Japanese Navies that utilize unique designs for the numbers 0 to 9.

You can still purchase these unique Japanese Number flags with model kits.  Note the Movement flags have been deleted in this image.  The flags are like stickers that fold up on the miniature flag poles.

SOURCE
http://dreadnoughtproject.org/friends/dickson/Complete_Signal_Book_version_2.pdf