That is a standard Airstream door hold back latch. It is still used for that purpose on the exterior of my coach too.
The old 1 piece slide latch was NLA a few years back, so this is the current solution. The newer trailers have a different spacing on the doors and use a Ventline door latch with an integral latch to hold the screen door closed.
There is also a slide latch that is available but it requires you to move it into position in order to use it. This way the door is automatically latched.
WBCCI #5501 AIR # 49
1978 Argosy 28 foot Motorhome
Wise men talk because they have something to say; fools, because they have to say something. -- Plato