Zip cords used to be common on small appliances here up until the 1960s/early 1970s. I have plenty of old radios, phonographs, lamps etc. as well as some test equipment which uses it.
There was also a 3-wire version used occasionally where a ground was required.
In the U.K., the 2-wire zip cord is also sometimes called "Figure 8", for the shape you see if looking directly at the cut end of the cord.
