Date is september 25th, 1965 or a few days later. During its last test flight, the nose “caved in” and flight crew barely manage to get home…see http://airpigz.com/blog/2011/1/9/1965-super-guppy-dive-test-goes-bad-not-a-bird-strike.html or http://f-bppa.blogspot.fr/2013/01/a-deux-doigts-de-la-catastrophe.html (in french) Reply
Guppy Photos 
Date is september 25th, 1965 or a few days later. During its last test flight, the nose “caved in” and flight crew barely manage to get home…see http://airpigz.com/blog/2011/1/9/1965-super-guppy-dive-test-goes-bad-not-a-bird-strike.html or http://f-bppa.blogspot.fr/2013/01/a-deux-doigts-de-la-catastrophe.html (in french)