Strange double line frame in some viewports when selected

On one file a strange double line (bluish and oragish) frame appears when the viewport is selected (bottom left) in the image
Any guesses?

you have the Safe Frame turned on. it is actually a dumb thing to have in Rhino since this is meant for film production, and since Rhino sadly has no real native animation abilities the whole thing does not make much sense. simply turn it off in the safe frame in your properties panels.

Thank you.
I have no idea how I accidentally turned it on.