Under the old system, examined patents were published pre-grant (this second publication stage was called 'kokoku'). The last kokoku were issued in early 1996. Kokoku numbers started from zero every new year, so the JPO issued them with an Emperor year prefix.
A 1995 examined patent issued by the JPO would look like this: h07-12345 B2.
From 1 January 2000 the Japanese Patent Office will use the four digit Gregorian year in their numbering systems rather than the two digit Imperial year.
So, a patent application (Kokai) which may currently appear as 08-231479A would be given in the future as P2002-231479A.
Patent applications Pyyyy-nnnnnn
Published patents Pyyyy-nnnnnnA (patents based on PCTs begin with Pyyyy-500001A) Pyyyy-nnnnnnA
