When the twelve digit numbering system for railway vehicles is introduced by the UIC and OSJD in the 1960s, the third and fourth digit represent the "owner" code as detailed bellow:

Europe:

05 - ICF - Intercontainer and Interfrigo (Switzerland)

06 - Stena Line Holland BV (Netherlands)

07 - IC - Intercontainer (Switzerland)

08 - Sealink (United Kingdom)

10 - VR - Finnish state railways (Finland)

12 - TF - Transfesa (Spain)

14 - CIWLT - Comp. International of Wagons-Lits and Tourisme (France)

15 - RMF - Rail Manche Finance (United Kingdom)

16 - HIPPS - Hermes International Planning and Production System (Switzerland)

18 - THL - Thalys International SCRL (Belgium)

19 - EUKL - Eurostar U.K. Limited (United Kingdom)
19 - ENS - European Night Service

20 - RŽD - Rossijskie Železnije Dorogi (Russia)

21 - BC - Belarusskaya Čygunka (Belarus)

22 - UŽ - Ukrzalyznicja (Ukraine)

23 - CFM - Calea Ferată din Moldova (Moldova)

24 - LG - Lietuvos Geležinkeliai (Lithuania)

25 - LDŽ - Latvijas Dzelzceļš (Latvia)

26 - EVR - Aktsiaselts Eesti Raudtee (Estonia)

34 - OHJ - Odsherreds Jernbane (Denmark)
34 - StLB - Styrian State Railways (Austria)
34 - PBr - Pont - Brassus (Switzerland)
34 - TRAVYS - Transport Vallée de Joux, Yverdon, Sainte-Croix (Switzerland)

35 - LJ - Lollandsbanen (Denmark)
35 - StH - Stern & Hafferl (Austria)
35 - RVT - Chemical regional fer of Val-de-Travers (Switzerland)
35 - TRN - Regioneaux neuchatelois (Switzerland)

36 - GFM - Gruyère - Fribourg - Morat (Switzerland)
36 - TPF - Fribourgeois transport publics (Switzerland)

37 - WLB - Wiener Lokalbahnen (Austria)
37 - STB - Sensetalbahn (Switzerland)
37 - TMR - Transports of Martigny and regions (Switzerland)

38 - RM - Regional transport Mittelland (Switzerland)

41 - HSH - Hekurudhat Shqiptare (Albania)

43 - GySEV - Raab - Ödenburg - Ebenfurther Eisenbahn (Hungary)

44 - BHÉV - Budapesti Helyiérdekk Vasút (Hungary)
44 - ŽRS - Željeznice Republike Srpske (Bosnia-Herzegovina)

45 - GKB - Graz - Köflacher Railway (Austria)
45 - SZU - Sihltal - Zurich - Uetliberg (Switzerland)

46 - MThB - Mittelthurgaubahn (Switzerland)
46 - THURBO - Thurgau - Lake Constance (Switzerland)

47 - SOB - Swiss Southeast Railway (Switzerland)
47 - CJ - Chemin de fer du Jura (Switzerland)

48 - BT - Lake Constance - Toggenburg Railway (Switzerland)
48 - SOB - Swiss Southeast Railway (Switzerland)

49 - RHB - Rorschach - Heiden Railway (Switzerland)

50 - DR - German Reichsbahn (German Democratic Republic - GDR)
50 - ŽBH - Željeznice Bosne and Hercegovine (Bosnia and Herzegovina)

51 - PKP - Polskie Koleje Panstwówe (Poland)

52 - BDŽ - B'lgarski D'ržavni Železnici (Bulgaria)

53 - CFR - Căile Ferate Române (Romania)
53 - SNCFR - Societatea Nationala de Cai Ferate Romania (Romania)

54 - ČSD - Československé Státny Dráhy (Czechoslovakia)
54 - ČD - České Dráhy (Czech Republic)

55 - MÁV - Magyar Államvasutak (Hungary)

56 - ŽSR - Železnice Slovenskej Republiky (Slovakia)

60 - CIÉ - Coras Iompair Éireann (Ireland)
60 - IE - Iarnród Éireann (Ireland)

62 - SP - Freight Wagon Association of Swiss Private Railways (Switzerland)
62 - ŽCG - Železnice Crne Gore (Montenegro)

63 - BLS - Bern - Lötschberg - Simplon (Switzerland)

64 - FNME - Railway North Milano Esercizio (Italy)

65 - RJB - Ryukkanbanen (Norway)
65 - MŽ - Makedonski Železnici (Macedonia)

66 - CIWL - Compagnie Internationale des Wagons-Lits

68 - AAE - Ahaus - Alstätter Railway (Germany)
68 - Bentheim Railway (Germany)

69 - Eurotunnel (United Kingdom)

70 - BR - British Rail (United Kingdom)
70 - EMS - English Welsh and Scottish Railway (United Kingdom)

71 - RENFE - Red National of the Spanish Ferrocarriles (Spain)

72 - JŽ - Zajednica Jugoslovenskih Železnica (Serbia)
72 - ŽS - Železnice Srbije (Serbia)
72 - HK - Hekurudha and Kosovës (Serbia)

73 - CH - Organismos Sidirodromon Ellados (Greece)

74 - SJ - Statens Järnvägar (Sweden)

75 - TCDD - Türkiye Cumhuriyeti Devlet Demiryollari Isletmesi (Turkey)

76 - NSB - Norges Statsbaner BA (Norway)

78 - HŽ - Hrvatske Željeznice (Croatia)

79 - SŽ - Slovenske Železnice D.D. (Slovenia)

80 - DB - Deutsche Bahn AG (Germany)

81 - ÖBB - Austrian Federal Railways (Austria)

82 - CFL - National Society of Chemins de Fer Luxembourgeois (Luxembourg)

83 - FS - Ferrovie dello Stato (Italy)

84 - NS - Netherlands Spoorwegen (Netherlands)

85 - SBB - Swiss Federal Railways (Switzerland)

86 - DSB - Danske Statsbaner (Denmark)

87 - SNCF - National Society of Chemins de Fer Français (France)

88 - SNCB - National Society of Chemins de Fer Belges (Belgium)

89 - ŽBH - Željeznice Bosne and Hercegovine (Bosnia and Herzegovina)

94 - CP - Caminhos de Ferro Portugueses E.P. (Portugal)


Other:

27 - KTŽ - Khazakhstan Temir Žoly (Kazakhstan)

28 - GR - Sakartvelos Rkynigza (Georgia)

29 - SAZ - Central Asian railways (Uzbekistan)
29 - UTY - Uzbekistan Temir Yullari (Uzbekistan)

30 - KRZ - State Railway Korea (North Korea)
30 - ZC - Zosen Chelto (North Korea)

31 - MTZ - Mongolyn Tömör Zam (Solonym) (Mongolia)

32 - DSVN - Duong Sat Viet Nam (Vietnam)

33 - KZD - Zhongguo Tie Lu (China)

40 - FC - Ferrocariles of Cuba (Cuba)

42 - JNR - Japan National Railways (Japan)
42 - EJRC - East Japan Railway Company (Japan)

57 - AŽ, ADY - Az Azrbaycan Dövllt D Dmir Yolu (Azerbaijan)

58 - ARM, ARŽ - Haykakan Yerkat Ughy, Armenskaja Železnica (Armenia)

59 - KRG - Kyrgyz Temir Žol (Kyrgyzstan)

61 - KNR - Korean National Railways (South Korea)

66 - TŽD - Rokhy Okhany Tochikiston (Tajikistan)

67 - TRK - Turkmendemiryollari (Turkmenistan)

90 - ENR - Egyptian National Railways (Egypt)

91 - SNCFT - National Society of the Chemicals of Fer Tunisian (Tunisia)

92 - SNTF - National Society of Ferroviaire Transport (Algeria)

93 - ONCFM - National Office of Chemins de Fer du Maroc (Morocco)

95 - IR - Israel Railways / Rakevet Jisrael (Israel)

96 - RAI - Rahahan-e Djomhouri-e Eslami Iran / Rah Ahan Iran (Iran)

97 - CFS - Chemins de Fer Syria (Syria)

98 - CEL - Office of the Chemin de Fer de l'Etat Libanais (Lebanon)

99 - IRR - Iraqi Republic Railways Establishment (Iraq)

From 2006, the third and fourth digit of the vehicle registration numbering no longer represents the owner code but the country code where the vehicle is registered.

Europe:

10 - FIN - Finland

20 - RUS - Russia

21 - BY - Belarus

22 - UA - Ukraine

23 - MD - Moldova

24 - LT - Lithuania

25 - LV - Latvia

26 - EST - Estonia

41 - AL - Albania

44 / 49 / 50 - BIH - Bosnia-Herzegovina

51 - PL - Poland

52 - BG - Bulgaria

53 - RO - Romania

54 - CZ - Czech Republic

55 - H - Hungary

56 - SK - Slovakia

60 - IRL - Ireland

62 - MNE - Montenegro

65 - MK - Macedonia

70 - GB - United Kingdom

71 - E - Spain

72 - SRB - Serbia

73 - GR - Greece

74 - S - Sweden

75 - TR - Turkey

76 - N - Norway

78 - HR - Croatia

79 - SLO - Slovenia

80 - D - Germany

81 - A - Austria

82 - L - Luxembourg

83 - I - Italy

84 - NL - Netherlands

85 - CH - Switzerland

86 - DK - Denmark

87 - F - France

88 - B - Belgium

94 - P - Portugal


Other:

27 - KZ - Kazakhstan

28 - GE - Georgia

29 - UZ - Uzbekistan

30 - PRK - North Korea

31 - MGL - Mongolia

32 - VN - Vietnam

33 - RC - China

40 - CU - Cuba

42 - J - Japan

57 - AZ - Azerbaijan

58 - AM - Armenia

59 - KS - Kyrgyzstan

61 - ROK - South Korea

66 - TJ - Tajikistan

67 - TM - Turkmenistan

90 - ET - Egypt

91 - TN - Tunisia

92 - DZ - Algeria

93 - MA - Morocco

95 - IL - Israel

96 - IR - Iran

97 - SYR - Syria

98 - RL - Lebanon

99 - IRQ - Iraq