Most analysts estimate that Iran has 140 working modified Mk3/5s left from the original 707 ordered in 1971 from Royal Ordnance (RO). It was originally envisioned that the total order would be for 1500 Chieftains delivered over a period of 10 years. The contract was valued at 650 million, but the Iranian Revolution cancelled these plans.
Many had been lost in the eight year-long Iran-Iraq War, while others were simply worn out or suffered from cooling problems. Attempts to smuggle British parts to Iran never seemed to succeed. While there has been Russian involvement in developing production facilities of Soviet-pattern armored vehicles in Iran, how much of this transfer of technology was involved in the Chieftain rehabilitation project is unknown (as is the number that Tehran can rehabilitate). - Adam Geibel
Colonel Zavari of the Iranian Army's ground forces Self-Sufficiency Unit told the Voice of the Islamic Republic on 25 September that his organization had been successful at reconditioned the army's Chieftain Main Battle Tanks (MBTs). They had changed the engine and power-transfer unit, designed and construct cooling, radiator and fan systems, as well as electric generators and motors for fans. These upgraded tanks were displayed at an exhibition of the Iranian Army ground forces' latest research and products that opened in Tehran on 23 July.