I'll respond because no one else did...
I don't have a lot of expertise on pins because I have never been a real collector. The plastic pins you mention began at WDW one year after the park opened with a cast member anniversary pin every year for the first twelve years. I'm not aware of any that were sold to guests, but maybe there were some.
Colorful pin back buttons were the big thing in the early years. The cast member birthday plastic pins were replaced by pin backs for the 14th WDW birthday.
The first cloisonnne pins that I can recall at WDW was about 1984, after the LA Olympics brought pin trading to the public.
Hope this helps a little...