I've had some of these, but never knew what they were...I believe they may have come in a small blister pack of 4 different figures in 1985 or so, just sort of as misc. memorabilia kinda like you see these days for the movies, but that's just conjecture =)
I have the megaton that you have pictured, misb. They were character erasers produced by a company called spindex, and there were 4 of these - the only one not in you pic is soundwave and they were sold separately. The same company also produced things like pencil cases, sharpeners, rulers etc. Hope this helps