This is a reupload, I wanted the relevant photos and only the unknown part highlighted. On November 07, 1993, at the William and Mary Hall, The College of William & Mary in Williamsburg, VA, Nirvana played a show where they ended with this jam before going into Endless, Nameless. It's definitely loose, and they are clearly jamming, but if you pay attention to the vocals and guitar, it sounds like Kurt has a verse section and chorus section, which he repeats, improvising in between. It sounds like a jam on an unfinished song to me, as their spontaneous jams usually don't have Kurt on vocals, and definitely not a whole chorus with singing and everything.
