While this album was eventually available at the online Cave shop on 25th August, both this album and Dodonpachi Daioujou arrange album
were already 'released' at the Cave Maturi on 15th August because 1) Cave didn't announce the online release until the Cave Maturi ended and only the leftover copies were sold at the online shop, 2) Cave didn't use words like prerelease (先行発売), which they used for Dodonpachi Daifukkatsu, and above all, 3) 15th August is Cave's official release date.
So I suggest we set this album's release date to 15th August, and add another Cave Maturi as an event to assign these two albums.
Cave Maturi are long-windedly named rather than just being numbered or dated like other events. 'ドキッ! ナースだらけのケイブ祭り ～ポロリは? ピーポーピーポー～
' was held on December 27th, 2008, and '監獄ケイブ祭り！来たら…逮捕しちゃうぞ
' was held on August 15th, 2009, but perhaps we don't need to literally translate them...