CREATE TABLE table_204_751 (id DECIMAL, "date" TEXT, "train" TEXT, "location" TEXT, "present location" TEXT, "comments" TEXT, "top speed  ( km/h ) " TEXT)

how many trains listed have the same speed as the hmb2 ?
SELECT COUNT("train") FROM table_204_751 WHERE "train" <> 'hmb2' AND "top speed (km/h)" = (SELECT "top speed (km/h)" FROM table_204_751 WHERE "train" = 'hmb2')
SELECT COUNT("train") FROM "table_204_751" WHERE "top speed (km/h)" = (SELECT "top speed (km/h)" FROM "table_204_751" WHERE "train" = 'hmb2') AND "train" <> 'hmb2'