CREATE TABLE table_25695027_1 (years_built VARCHAR2, cylinder_size VARCHAR2, firebox VARCHAR2)

This engine with a cylinder size of 20 x 26 and a firebox of radial-stay was built when?
SELECT years_built FROM table_25695027_1 WHERE cylinder_size = "20 ½” x 26”" AND firebox = "Radial-stay"
SELECT "years_built" FROM "table_25695027_1" WHERE "20 ½” x 26”" = "cylinder_size" AND "Radial-stay" = "firebox"