It came with a book of projects (e.g. 150 projects and hence the toy's name) and each page had a listing showing the wires you attach from one coiled spring to another. Hook up different components of the board to make an AM radio receiver, or a "lie detector", or tone generator.
Here's the crazy thing. I ran across an old one 20 years later as an adult and the toy's brilliant idea finally dawned on me: it allows small children to play with electronics without getting burned by a hot 700 degree soldering iron! Instead, the child's fingers push the springs apart and he inserts the pre-stripped wires to connect it to another spring. It was even genius that all the wires it came with were pre-stripped so that even wire cutters weren't necessary. Everything was also low voltage (9v & 1.5v batteries) so you didn't have to worry about a naked power supply plugged into the wall electrocuting the kid. (E.g. https://youtu.be/9RMKrpzoMkE?t=2m52s)
My kit had diodes on it but unlike the author, the toy didn't teach me about them. Perhaps for others, the Radio Shack kit was a gateway drug to an electronics career.