Question: When did the maker of the Acura Legend, the manufacturer of Toyopet Master, and Nissan open US assembly plants?

Knowledge 1: Toyopet Master
The Toyopet Master range also included the Masterline RR16 pickup, the Masterline RR17 van and the Masterline RR19 double pickup (with two rows of seats). They were introduced in November 1955, originally only as a single-cab pickup and a van. The double pickup was added in August 1956, around which time the engine was upgraded to provide . These replaced the SG commercial models and were the first car-based trucks to enter production in Japan. The Masterline commercial models were carried over after the discontinuation of the Master. They were built until replaced by a new Crown-based Masterline in March 1959, for the Toyota Store sales channel. A smaller Coronaline version was also developed to be sold through Toyopet dealers. [SEP] Knowledge 2: 1973 oil crisis
Some buyers lamented the small size of the first Japanese compacts, and both Toyota and Nissan (then known as Datsun) introduced larger cars such as the Toyota Corona Mark II, the Toyota Cressida, the Mazda 616 and Datsun 810, which added passenger space and amenities such as air conditioning, power steering, AM-FM radios, and even power windows and central locking without increasing the price of the vehicle. A decade after the 1973 oil crisis, Honda, Toyota and Nissan, affected by the 1981 voluntary export restraints, opened US assembly plants and established their luxury divisions (Acura, Lexus and Infiniti, respectively) to distinguish themselves from their mass-market brands. [SEP] Knowledge 3: Acura Legend
The Acura Legend is a mid-size luxury/executive car manufactured by Honda. It was sold in the U.S., Canada, and parts of China under Honda's luxury brand, Acura, from 1985 to 1995, as both a sedan, which was classified as a full-size car, and a coupe, which was classified as a mid-size car (similar to how the Honda Accord is set up today). It was the first flagship sedan sold under the Acura nameplate, until being renamed in 1996 as the Acura 3.5RL. The 3.5RL was the North American version of the KA9 series Honda Legend.
Knowledge 1: 1973 oil crisis
Some buyers lamented the small size of the first Japanese compacts, and both Toyota and Nissan (then known as Datsun) introduced larger cars such as the Toyota Corona Mark II, the Toyota Cressida, the Mazda 616 and Datsun 810, which added passenger space and amenities such as air conditioning, power steering, AM-FM radios, and even power windows and central locking without increasing the price of the vehicle. A decade after the 1973 oil crisis, Honda, Toyota and Nissan, affected by the 1981 voluntary export restraints, opened US assembly plants and established their luxury divisions (Acura, Lexus and Infiniti, respectively) to distinguish themselves from their mass-market brands. [SEP] Knowledge 2: Acura Legend
The Acura Legend is a mid-size luxury/executive car manufactured by Honda. It was sold in the U.S., Canada, and parts of China under Honda's luxury brand, Acura, from 1985 to 1995, as both a sedan, which was classified as a full-size car, and a coupe, which was classified as a mid-size car (similar to how the Honda Accord is set up today). It was the first flagship sedan sold under the Acura nameplate, until being renamed in 1996 as the Acura 3.5RL. The 3.5RL was the North American version of the KA9 series Honda Legend. [SEP] Knowledge 3: Toyopet Master
The Toyopet Master range also included the Masterline RR16 pickup, the Masterline RR17 van and the Masterline RR19 double pickup (with two rows of seats). They were introduced in November 1955, originally only as a single-cab pickup and a van. The double pickup was added in August 1956, around which time the engine was upgraded to provide . These replaced the SG commercial models and were the first car-based trucks to enter production in Japan. The Masterline commercial models were carried over after the discontinuation of the Master. They were built until replaced by a new Crown-based Masterline in March 1959, for the Toyota Store sales channel. A smaller Coronaline version was also developed to be sold through Toyopet dealers.
Knowledge 1: 1973 oil crisis
Some buyers lamented the small size of the first Japanese compacts, and both Toyota and Nissan (then known as Datsun) introduced larger cars such as the Toyota Corona Mark II, the Toyota Cressida, the Mazda 616 and Datsun 810, which added passenger space and amenities such as air conditioning, power steering, AM-FM radios, and even power windows and central locking without increasing the price of the vehicle. A decade after the 1973 oil crisis, Honda, Toyota and Nissan, affected by the 1981 voluntary export restraints, opened US assembly plants and established their luxury divisions (Acura, Lexus and Infiniti, respectively) to distinguish themselves from their mass-market brands. [SEP] Knowledge 2: Acura Legend
The Acura Legend is a mid-size luxury/executive car manufactured by Honda. It was sold in the U.S., Canada, and parts of China under Honda's luxury brand, Acura, from 1985 to 1995, as both a sedan, which was classified as a full-size car, and a coupe, which was classified as a mid-size car (similar to how the Honda Accord is set up today). It was the first flagship sedan sold under the Acura nameplate, until being renamed in 1996 as the Acura 3.5RL. The 3.5RL was the North American version of the KA9 series Honda Legend. [SEP] Knowledge 3: Toyota
From September 1947, Toyota's small - sized vehicles were sold under the name ``Toyopet ''(トヨペット). The first vehicle sold under this name was the Toyopet SA, but it also included vehicles such as the Toyopet SB light truck, Toyopet Stout light truck, Toyopet Crown, Toyopet Master, and the Toyopet Corona. The word`` Toyopet (Japanese article)'' was a nickname given to the Toyota SA due to its small size, as the result of a naming contest the Toyota Company organized in 1947. However, when Toyota eventually entered the American market in 1957 with the Crown, the name was not well received due to connotations of toys and pets. The name was soon dropped for the American market, but continued in other markets until the mid-1960s.

Answer: 1981