I purchased my set of Sailor Ink Studio inks (all 100) from Pen Classics in New Zealand. These Ink Studio 100 are based on the Ink Studio custom inks blended by Ishimaru that are held at events around Japan throughout the year. These 100 are chosen, somehow, from the the the thousands of custom blends that people have asked the inkmeister at these events to make for them. As for the numbering, there is certainly patterns about them and they aren’t randomly numbered.