Thread:Nagumo baby/@comment-124.253.206.137-20131124093508/@comment-3200351-20131124105014

I found a website that says the OVA was first distrubted as a prize as part of the Goemon 5th anniversary campaign in 1991. Therefore, it has no offical release date.

http://entertainment.rakuten.co.jp/contents/0000024906/

I hope that helps.