This engine with a cylinder size of 20 ½” x 26” and a firebox of radial-stay was built when?
create table table_25695027_1 (years_built varchar, cylinder_size varchar, firebox varchar, PRIMARY KEY (years_built))
select years_built from table_25695027_1 where cylinder_size = "20 ½” x 26”" and firebox = "radial-stay"