user: Question: What is the average year for Wallenstein with 1A1 design?
Columns: ['Name', 'Design', 'Manufacturer', 'Acquired', 'Disposed']
Types: ['text', 'text', 'text', 'real', 'text']
Sample row: ['Adler', '1A1', 'Stephenson 1835', 1835.0, 'sold 1857']
SQL:

assistant: SELECT AVG("Acquired") FROM "Table" WHERE "Design" = '1A1' AND "Name" = 'Wallenstein';