This is a sleeve designed to hold and protect common 3" x 5" memo book pads.
Also see…
https://www.printables.com/model/460960-rocketbook-mini-sleeve
I printed using PLA at 0.2mm layer height with a 5mm brim. Orientate the print with the small bottom face on the bed as shown in the photo.
The author marked this model as their own original creation.