CREATE TABLE table_203_27 (id DECIMAL, "number" DECIMAL, "serial no" DECIMAL, "entered service" TEXT, "withdrawn" TEXT, "kilometres travelled" DECIMAL)

when was number 4102 entered into service ?
SELECT "entered service" FROM table_203_27 WHERE "number" = 4102
SELECT "entered service" FROM "table_203_27" WHERE "number" = 4102