A processing device and method for processing a stack of bags having a multitude of open-mouth bags are provided, including a stacking device on which the stack of bags can be disposed in a base position, wherein the open-mouth bags of the stack have a bag length and an open filling mouth at one end. A marker device and a bag conveying device are provided that are suitable and provided for gripping the topmost open-mouth bag of the stack in the base position and displacing it to a take-up position that is only partially supported on the stack of bags and putting at least one mark on the open-mouth bags in the take-up position.