Microwave oven
In 1947, Raytheon built the "Radarange", the first commercially available microwave oven. It was almost tall, weighed and cost about US$5,000 ($ in dollars) each. It consumed 3 kilowatts, about three times as much as today's microwave ovens, and was water-cooled. The name was the winning entry in an employee contest. An early Radarange was installed (and remains) in the galley of the nuclear-powered passenger/cargo ship NS "Savannah". An early commercial model introduced in 1954 consumed 1.6 kilowatts and sold for US$2,000 to US$3,000 ($ to $ in dollars). Raytheon licensed its technology to the Tappan Stove company of Mansfield, Ohio in 1952. They tried to market a large 220 volt wall unit as a home microwave oven in 1955 for a price of US$1,295 ($ in dollars), but it did not sell well.
Sandwich
It has been suggested that UK's first pre-made packaged sandwiches were sold by Marks & Spencer in 1980. As they proved wildly popular, a small experiment involving five stores rapidly grew to cover more than one hundred stores. Within a year, the store was looking for ways to manufacture sandwiches at an industrial scale.
However, the first pre-packed sandwiches date from well before this. British Home Stores sold pre-packed sandwiches in the 1960s (see the Radio Times 3 November 2018 p.167), and earlier even than that, Marks and Spencer (Brighton branch) began selling them in the 1950s, and then in the 1960s in the Oxford Street branch, London. (See the Radio Times 10 November 2018 p.160)