Only the current version so far — new entries appear as the app ships updates.
Reader™ビューワープラグイン(旧フォーマット用) is a books & reference app by Sony Music Entertainment (Japan) Inc. with 10,000+ downloads (about 21K estimated). +2 installs in the last 7 days. Install growth, rank history, SDKs and ad networks.
From the store listing: “Reader is a plug-in used to display the book for the "e-book Reader ™ Sony" in the old format (XMDF format / dot book format) of the Store.”