Vent Window Division Bar Question/Help

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Starting the next phase of updates to my '64 C10 with some way overdue weatherstrip upgrades and found something odd with the drivers division bar. Unlike the passenger's side that just has the deteriorating felt in the stock frame, this one has what appears to be a secondary/rigid metal insert with a corrugated surface that I assume was part of maybe an earlier replacement??

I am trying to figure out my plan before tearing things apart as I want to hold off going through the vent window itself until winter. I know it has to come out anyways to swap the fuzzy insert, but trying to gauge what I might find before getting started.

Drivers side is the first photo.

Thanks!