From what I have heard it was version 2.0 where it became popular. I recall reading from an excellent set of After Dark articles on LEM that the modules we all know and love came about in 2.0.
I just grabbed an AD 2.0 disk and the label says ©1990. It went through a ton of revisions in 2.0 form--I think 3.0 came out around 1994. Four years is a lot of time to popularize software, especially software with flying toasters as a screen saver module.
I don't think 1.0 was out for too long, so you may have yourself a collectible.