An image processing apparatus having an adding unit to add information by changing a data value of image data and a detecting unit to detect the information added to the image data. The aim of the invention is to develop a design which enables a high power density at high magnetic reversal frequencies and which is easy to produce. Outer edges of the first and second rectangular-shaped sheet portions are coupled together such that an interior region is formed between the first and second rectangular-shaped sheet portions. A tab on the front of the vertical divider engages with a slot in the front wall of the swingable front portion when the front portion is in the closed position for adding rigidity to the enclosure when the front portion is closed.