CREATE TABLE table_54951 ("Class" TEXT, "Wheel arrangement" TEXT, "Fleet number ( s ) " TEXT, "Manufacturer" TEXT, "Year made" TEXT, "Quantity made" TEXT, "Quantity preserved" TEXT, "Year ( s )  withdrawn" TEXT)

What is the fleet number of the locomotive with 1 quantity made?
SELECT "Fleet number(s)" FROM table_54951 WHERE "Quantity made" = '1'
SELECT "Fleet number(s)" FROM "table_54951" WHERE "Quantity made" = '1'