Abbott Mysteries started in 1945 and ran during the summers until 1947.  A revival "The Adventures of the Abbotts" started up in Oct on the 3rd in 1954 and ran every  sunday at 8:30 until june 12, 1955.  So the complete broadcast history would  have to include each sunday from Oct 3rd, 1954 until June 12, 1955.  It is  conceivable that the Otter volunteer who took on the Abbotts log knows about some shows which are suppose to be available that he or someone he knows has in their collection but only knows the dates and no show titles.  While I thought Otter was suppose to weed out speculations in collections and authenticate the episodes  entered in to the database, it appears at first glance that someone took the 1955 dates, counted the Sunday dates up to June 12th and decided that these must  have existed. However if Dunnings Encyclopedia of OTR is correct, Then the OTTER database hasn't logged the entire 1954 run of the show.