Table: railcars_gwr
Columns: number_range
introduced
builder
engine
seats
withdrawn

Question: What date was introduced where it was withdrawn 1955?
SQL: SELECT "introduced" FROM railcars_gwr WHERE "withdrawn" = '1955'

Question: What engine was introduced in 1935?
SQL: SELECT "engine" FROM railcars_gwr WHERE "introduced" = '1935'

Question: What is the number range for the Gloucester RCW builder introduced in 1937?
SQL: SELECT "number_range" FROM railcars_gwr WHERE "builder" = 'gloucester rcw' AND "introduced" = '1937'