Question: What is the name of the second generation battle tank whose origin is a unitary parliamentary democracy and constitutional monarchy ?

text: List of main battle tanks by generation
Second generation
The second generation had enhanced night-fighting capabilities and in most cases NBC protection . Most western tanks of this generation were armed with the 105 mm Royal Ordnance L7 tank gun or derivatives of it .
Main battle tanks are often classified as belonging to a particular generation, although the actual definition and membership in these generations is not clearly defined. Soviet and Russian military planners organize tanks with first generation of tanks up to 1945, and four generations of main battle tanks[Note 1] while Canadian strategists organize main battle tanks into three generations. [Note 2] The military of the People's Republic of China also recognizes three generations of its own tanks. In 1983, Rolf Hilmes saw three tank generations and three intermediate generations, which consisted mainly of upgraded vehicles. The first generation of main battle tanks were based on or influenced by designs of World War II, most notably the T-34 and the Panther tank. The second generation was equipped with NBC protection (only sometimes), IR night vision devices, a stabilized main gun and at least a mechanical fire control system. The third generation is determined by the usage of thermal imagers, digital fire control systems and special (composite) armour. However, Hilmes acknowledged that tanks cannot be definitively grouped by generations, as each tank-producing country develops and introduces its tanks in tune with its own ideas and needs. He also states that breakdown of postwar tanks by generations is based on timeframe and technical factors, as a basis for further discussion.
Name Entered service in Origin Notes
T-62 1961 Soviet Union A further development of the T-55
M60 Patton 1961 United States A further development of the M48 Patton tank . Later models ( M60A2 and M60A3 ) are considered as the first intermediate generation
Leopard 1 1965 West Germany A main battle tank designed and produced in West Germany that first entered service in 1965
Panzer 61 1965 Switzerland A further development of the Panzer 58 tank
MBT-70 1965 United States / West Germany An American-West German joint project to develop a new main battle tank . Never entered service
T-64 1966 Soviet Union World 's first composite armored tank , later versions of the T-64 may be considered as third generation
AMX 30 1966 France The AMX 30 served as the principal Main Battle Tank ( MBT ) for the French Army
FV 4201 Chieftain 1966 United Kingdom Armed with the British 120 mm Royal Ordnance L11A5 gun
Vickers MBT 1967 United Kingdom British private venture design for export , licence built as the Vijayanta for India
Stridsvagn 103 1968 Sweden Turretless design developed and employed solely by Sweden . Double engine feature ; both diesel and gas turbine
Panzer 68 1971 Switzerland Swiss Main Battle Tank ( MBT ) based on the Panzer 61
T-72 1973 Soviet Union Hilmes puts the T-72 in the first intermediate generation
Olifant Mk 1 1974 South Africa A further development of the Centurion Tank
Type 74 1975 Japan Hilmes puts the Type 74 in the first intermediate generation
Merkava Mark I 1979 Israel First Main Battle Tank developed and used by Israel Defense Forces
Ch'onma-ho 1980 Soviet Union / North Korea Copy of the T-62 ; later versions include upgrades
OF-40 1981 Italy Main Battle Tank used by United Arab Emirates
Tanque Argentino Mediano 1983 Argentina Argentine Medium Tank developed from Marder IFV by Argentina and Thyssen-Henschel
Merkava Mark II 1983 Israel Improved Merkava Mark I
T-55AM 1985 Soviet Union / Czechoslovakia T-55 with new engine , FCS computer , BDD composite armor ( later active armor or ERA ; T-55AMV , T-55AMD ) , equipped with new APFSDS ammunition ( BM-20 or BM-25 ) . Frontal protection of T-55AM with BDD add-on equals first T-72s