CREATE TABLE table_21741 ("Number" TEXT, "Builder" TEXT, "Type" TEXT, "Date built" TEXT, "Heritage" TEXT, "Disposition" TEXT, "Notes" TEXT)

Name the builder for date built is january 1910
SELECT "Builder" FROM table_21741 WHERE "Date built" = 'January 1910'
SELECT "Builder" FROM "table_21741" WHERE "Date built" = 'January 1910'