Question about rear window channel?

[Back N Black]

I pulled the window channels from my doors and one side has the plastic guide, as per the pic below and the other channel has no guide. The felts look original and there is no cut out to indicate that there was a plastic guide on the channel. Was it something that was introduced mid year.One door is original to the car and the other is from another car(both 69 doors).

Thanks mike for the use of your pic

[Shakey]

You got me there.  Maybe Chris, Doug or Geno know.

[rare69]

I don't know for sure, but both my original doors don't have the plastic pieces and never had them.its a very early built car also.