Trivial Tuesday

Look below for three posts since Monday Welcome to another exciting edition of Trivial Tuesday with another geeky twist.  I'm not sure how easy it is, but I'm going to ask anyway.  The answer, regardless, will be revealed on Friday, along with a little comparison between then and now.
The first one of these was sent May 3, 1978 to about 600 people.  What was it? As a bonus, what was it regarding?  I doubt anybody will get this part.
There you have it.  I figure the first part will be simple, but the bonus will take a true geek to know.  Thanks for playing, and I will have the answer on Friday.