user: Question: When was the train 2053 built?
Columns: ['Serial number', 'Wheel arrangement ( Whyte notation )', 'Build date', 'Operational owner(s)', 'Disposition']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['unknown', '4-4-0', 'October 1856', 'Western and Atlantic Railroad #49 Texas', 'static display in Grant Park , Atlanta, Georgia']
SQL:

assistant: SELECT "Build date" FROM "Table" WHERE "Serial number" = '2053';