SELECT "Class" FROM table_70761 WHERE "Quantity made" = '1' AND "Type" = '0-6-0t'
What is the class of the locomotive with a quantity made of 1 and a 0-6-0t type?
CREATE TABLE table_70761 (
    "Class" text,
    "Type" text,
    "Names" text,
    "Quantity made" text,
    "Manufacturer" text,
    "Date made" text
)