A rotary piston and cylinder device (1) comprising a rotor (2), a stator and a shutter disc (3), the rotor comprising a piston which extends from the rotor into the cylinder space, the rotor and the stator together defining the cylinder space, the shutter disc passing through the cylinder space and forming a partition therein, and the disc comprising a slot (3a) which allows passage of the piston therethrough, the shutter disc comprising a circumferential surface (30) arranged to form a seal with a surface of the rotor, the circumferential surface defining a profile which forms at least one close running line (13b) with said rotor surface, and the at least one close-running line offset from a rotor plane (13) which lies on a radius of the rotor and which includes the axis of rotation of the rotor.