Question: Which owner has a description of Mark 1 POS and is dated 1956?
SQL: SELECT "Owner(s)" FROM "2-11913905-7" WHERE "Date" = 1956.0 AND "Description" = 'Mark 1 POS';

Question: Which owner has a description of Mark 1 CK and is dated 1953?
SQL: SELECT "Owner(s)" FROM "2-11913905-7" WHERE "Date" = 1953.0 AND "Description" = 'Mark 1 CK';