As of 2017 what was the most-produced tank in military history?

The T-54 and T-55 tanks and variants were produced by the Soviet Union beginning in 1946. Based on earlier tank designs of the T-34 (the most produced tank during WW II) and T-44, it was armed with a 100mm main gun and weighed in at 36 metric tons. The T-54 and T-55 tanks were produced in the Soviet Union through 1981, and Warsaw Pact countries, such as Poland and Czechoslovakia were licensed to produce the tanks as well. When production ceased in the 1980s, an estimate of between 86,000 and 100,000 units were manufactured.

The T-54/T-55 tanks were operated by as many as 50 countries across the globe, including Chile, Iraq, Egypt, North Korea and the successor states to the Soviet Union. Countries such as Mongolia and Peru as recently as 2006 still had T-54/T-55s in front-line service. As recently as 2013, Ukrainian companies were reportedly developing T-55 upgrades targeting the export market.