Ervin, could you show a photo of the other window? I mean - the one with the chrome still on it. This issue (whether chrome trimmed vent windows ever actually existed) is a mystery and a subject of debate
None of the square body people that I know - up here in New England - has ever seen vent windows as you describe (with a dividing strip that is chromed or have a chrome cover). I have seen this feature mentioned several times, but can't find any real evidence that they were ever actually available.
My old truck (86 K20 Sierra Classic) came loaded with a full YE9 trim package and was always kept in bone stock condition. The vent window dividing pillar - as well as the rest of the frame - on that truck was flat black:
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