There is no listing for a 4/9/67 performance at Longshoremen's Hall. At least two posters/handbills exist for this show but only one has the GD billed and that looks like a late addition.
One can be seen at http://www.deadlists.com/posters/1960s/19670409a.html This is the one that has the GD added apparently at the last minute. A different one can be viewed at http://www.sixtiesposters.com/images/longshoremans04091967.jpg This one doesn't indicate the GD but it refers to the concert as a benefit for Angry Arts Week. The ebay auction here http://tinyurl.com/4m3zu has a handbill for a concert at the end of Angry Arts Week on 4/11/67 (GD didn't perform). The seller indicates "ON THE BACK IS LISTED A WEEKS WORTH OF EVENTS LEADING UP TO A PEACE MARCH IN SAN FRANCISCO. SOME OF THE FEATURED ACTS WERE THE GRATEFUL DEAD, SOPWITH CAMEL, COUNTRY JOE AND THE FISH AND QUICKSILVER." Can this show be added to deadlists? Iver