For applications filed before 1 January 2002, the following numbering system applies:

The application number consists of nine digits. The first two digits (from left to right) of the application number indicate the filing year. The last (ninth) digit is a check digit. The third digit or third and fourth digits of the application number indicate(s) the place of filing.

The remaining digits are used for consecutively numbering the applications in the order in which they come in at the place of filing.

International applications filed under the Patent Cooperation Treaty (PCT), and designating "EP" (Euro-PCT applications) receive the digit "9" as the third digit or the digits "27" as the third and fourth digits.