drip rail cracks?

[Moosestang]

I'm looking at cars and seeing a lot of cracks in the drip rail channels. is this some sort of seam sealer that is painted over or something else? I'm concerned about hidden rust so i past on several because of it. It just looked like a crack in the paint over metal, but the chrome has to connect to the roof somehow correct? Anyone have a restoration pic with all the paint removed so i can understand what's going on there?:yesnod

 

[Yadkin]

In my 64 its an elastomeric product; probably seam sealer. The stainless trim is snap fit onto the outer edge of the channel.