user: Question: What was the issued serial for yellow on blue design issued in 1955?
Columns: ['Issued', 'Type', 'Design', 'Serial format', 'Serials issued']
Types: ['real', 'text', 'text', 'text', 'text']
Sample row: [1954.0, 'Passenger', 'black on orange', 'AB 123', 'unknown']
SQL:

assistant: SELECT "Serials issued" FROM "Table" WHERE "Design" = 'yellow on blue' AND "Issued" = 1955.0;