The following are dates listed here along with dates I wrote down from ebay auctions:

275 5/15/69
275 6/17/69
275 7/11/69
275 7/22/69
275 7/29/69
275 9/24/69

276 7/15/69
276 8/20/69
276 9/25/69
276 10/26/69
276 11/3/69
276 11/11/69
276 12/9/69
276 12/11/69
276 12/22/69