Very useful info man, thanks.
Reading through (some of) what's in that link I found a listing under Glossary of Cymbal Types/Hi Hats...for flange hi hats.
It says they are "an unusual pairing of a specially tapered medium heavy top cymbal and a heavy bottom cymbal which has a 2" flanged outer edge".
Hmmm. Never seen them in these here parts. the wording has me thinking that only the bottom cymbal has the flange.
If anyone has any experience with those, I'd love to hear it.