Throat grommets, St V vs Chicago

[aimr75]

I have been doing a number of searches learning about St Vincents, but wanted to ask about the flat versus raised throat grommets

Did the flat throat grommets exist on the chicago models and cross over to the St Vincent bumperless?

Can there be models of chicagos and st vincents that exhibit very close characteristics to the point where you couldnt distinguish? were there any chicago's with XXQ codes?

If i'm completely off base, let me know as far as chronology
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[PrestigeClassic]

River Grove, Illinois: convex grommets, no bumper
First year St. Vincent: convex grommets, no bumper
After first year St. Vincent: flat grommets, yes bumper

Tried fitting flat throat grommets onto a frame that came with convex grommets and as I recall it was a no go. Others have stated the head grommets aren't exactly interchangeable either.

During the initial year of Pro Staff Midsize production, I've found there to be some variance in the appearance of the frames, such as paint gloss amount. A lot of River Grove frames are matte like St. Vincent and are similar in appearances. I've also found every bumperless model that I've tried played like crap anyway. Even the convex throat grommets sometimes became brittle. As you can imagine, as happens within other industries, Wilson got it right after a short while.