I've been right through that little town a 100 times over the years (it's on the long, instead of the short way out of town to horse country). But I've never heard of this event at all, and I ride from time to time with the Fairfax (County) Chapter of SCRC, and never heard about it from any of them either. Clifton is a nice little sleepy town (19 miles from my house), and also has several fairs/bazaars every summer, and can be a big mistake to ride into those traffic jams (which I have also done).
I had no idea there were even that many vintage machines around here.
Thanks for the pics post.

I'm definitely going to look into attending one of these.
I've even had lunch here:

And right across the street here:

The little town is deceiving, there's some big money out there, scroll down.
https://www.google.com/search?q=clifton+va&client=firefox-b&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjN2uC916zaAhVF7oMKHU4ZDwcQ_AUIDSgE&biw=1424&bih=652