Neither drivers or passengers doors have anything in that slot. Door glass hasn't been touched since I bought car from orig owner in 1979. I have another spare complete clean '69 door doesn't have it either. In another thread it was stated in '69 they put an up stop that mounts to rear of glass as shown here. The rear up stop does go up and contact an arm on the rear channel. Rear of glass rest up against roof weather strip correctly.
Also, this window not going all the way up issue has been there since 1979 when I bought car. Would like to correct to get rid of wind noise from glass not being all the up.
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