'Preppy' was funny stuff... The Bean Boot is a big hunk of rubber with a leather top, the Down Vest was made from very un-natural fibers... They banned Purple & Velour - both happily embraced by Brooks Bros back in the day...

I'd put in my first 3 and a bit years of Ivy obsessiveness before the OPH came out & I thought very little of it on sight. Maybe I was just too serious for its froth. And, Lord knows, I was a serious boy back then...

Had 'Trad' not been based on the 'Preppy' dilution of my beloved Ivy that I so detested I might have been kinder to it. I guess we all have a certain amount of 'baggage' that we bring with us to any subject...

Oh yes...  the down vest...  forgot about that...  I have indulged myself...  £10...

Although... You can argue that the satiric 'rules' of the OPH are the primary source for 'Preppy' & that the Trollish  writings of Harris (stolen from Horace & misrepresented) are the primary source for 'Trad'...

Which is to say that both styles are not Ivy (hence their different names!) and cannot be confused with the parent Classic Traditional American style - The Ivy League look.

Preppy & Trad are just later fashions. Which makes absolute sense.

Traditional American is neither of those two things, it's bigger.

To be honest, Uncle, I was so pig-ignorant to begin with I completely failed to make the Monty Clift/Brooks/Ivy connection with what I was wearing - which I heard described (by a jazzhead friend of the old feller's) as 'preppy'.  Kind of spoiled it for me.