A metal plate is connected to a wall. At least one of the scroll members disposed in the shell is mounted for axial movement with respect to the other scroll member disposed in the scroll. When the cover member is positioned at the cover position, the recording is permitted on a recording paper sheet accommodated in a recording paper-accommodating mechanism. Similarly, the detection system lug includes a groove that receives the point detector connecting rod and that permits a slight degree of pivoting therebetween while remaining securely mounted thereto.