CREATE TABLE table_name_73 (fleet_size VARCHAR2, class VARCHAR2)

What is the fleet size of the Vanguard 0-6-0dh class?
SELECT fleet_size FROM table_name_73 WHERE class = "vanguard 0-6-0dh"
SELECT "fleet_size" FROM "table_name_73" WHERE "class" = "vanguard 0-6-0dh"