Tonearm evolution

Trying to learn about the evolution of the tonearm and would love anyone to chime in on historical milestones.

My first question is who were the first to drop the counterweight?

I have an AudioCraft AC-300 which has slightly lowered counterweight and that is the precursor to the later models that dropped the counterweight way down and was copied (I believe) by others.

Just curious
Have a butcherse at the high end audio website of Artur Salavatore - it has a good history of tonearms
Thanks. I've read his blog several times. He goes through a lot of arms but really just states his opinion on the sound. I was looking for a more historical time-line from a technical stand point, i.e. "Who was the first to use a straight arm tube? Wanted to get a thread going so people had something to refer to, but this might not be the place to do so.