huinventors1-2, Exercise 3: Idea, builder, success

Model answer:

Rubik: the idea and the working build in Budapest (a prototype in 1974, patent applied for in 1975), plus the Hungarian patent.
Ishigi: a Japanese inventor said to have patented a similar mechanism in 1976, an independent builder whose version did not become famous (check).
Ideal Toy: success, by licensing and launching the cube worldwide in 1980 (check).

The example shows that the first to have an idea, the one who builds it and the one who makes it succeed need not be the same person. Details should be checked.