When the original Spider Man cartoon premiered in 1967, each episode ended with a bumper containing previews for next week’s episode. When the show was syndicated these bumpers were removed as they were considered non-important and confusing considering episodes could air out of order.
I’m not sure how long these bumpers lasted but I’m assuming the whole first season would have them at least. It seems as though they are mostly lost though unfortunately due to their removal early on and are not available on any of the VHS or DVD releases of the show.