The 2 digit country code is based on the old 2 digit railway code. The code is defined in the UIC/OSJD OSJD Organisation for the Collaboration between Railways (OSZhD) Leaflet 920-14 – Version 2 (March 2005). This leaflet exists in 3 languages:
The table now also includes the code 49 for Bosnia and Herzegovina. This has become necessary as Bosnia and Herzegovina is joining the international seat reservation system. The codes 44 and 50 for the Serb Republic and the Muslim-Croat Federation may still be used on existing applications.