I am asking for opinions here not production or sales figures- having said that, why do you feel that the Cox "La Cucaracha" was so beloved in period and even today?
From "Slot Car History" website:
"The greatest name in vintage slot cars was Cox. The company was founded by L.M. "Leroy" Cox of Santa Anna, California in 1945. Cox Manufacturing whose main lines involved the production of miniature gas-powered internal combustion engines along with control line model aircraft, created in 1947 the Thimble Drome Champion, the car that help start the tether car craze.
In 1964 they joined the slot car business with some high quality kits initially featuring die cast magnesium chassis. With their box art and attention to detail they are now much sought-after toys which they produced until 1969. The Ferrari 158 F1 assembled in Hong Kong for the American company was the first RTR model marketed by Cox. When Cox issued the orange low-slung slot car known as "La Cucaracha" or, "the cockroach", it created a small revolution in the slot car world. The car was fast, out-handled most of its production competitors."