This song has been floating around on the Internet since 1998.  It's still under debate whether or not this song is performed by Nirvana, or a Nirvana satellite band (The Retards).  It's an instrumental song that song lasts 110 seconds, and is always accompanied with "recorded at the Melvins' house."

If that's the case, then it could have been recorded in April of 1991.  The circulating information on this song is all speculation.  However, it does bare resemblance to "Unknown Jam 1991.12.04 #1".