Thanks for the extra information, R.Cates.
Two things must be established if you like to have it visible after frame 160 while it starts at frame 160 with its frame one plus starts to be visible.
(1) Range Start needs to be at 160, and (2) you need to animate the use of that Material.
The easiest way to animate the use of a Material is via animated Selections (Attribute Manager> Material Tag) or animated the content of the Alpha channel, e.g., with a Color Shader.
The interface of the animation parameter might be confusing. It is simple when you remember: Range is for the playtime in the editor (It is always visible, but when it starts and stops (playing/running) is based on the Range.
What part of the movie clip is played are the two parameters below: Movie Start and Stop, like cutting start and end away.
This duration of the movie will then fill the Range. You can even play a movie backward: Movie Start number must be higher than the Movie End.
If you need an example, please let me know.