The disc came with Dengeki PS2 Vol. 275, sealed inside a cardboard page. Two different jewelcase sized back inserts could be cut out from the magazine.
It contains a playable demo of Silent Hill 4 The Room. (It also contains Kuon save data, but as it is not official contents this page is not listed in that section.)
1. Front of magazine
2. Disc page
Thanks to Lin (images 1-3).