CREATE TABLE table_1976 ("Number" TEXT, "Previous Number ( s ) " FLOAT, "Previous Class" TEXT, "Converted" FLOAT, "Use" TEXT, "Withdrawn" FLOAT, "Disposal" TEXT)

What is every previous class when the previous number is 61323?
SELECT "Previous Class" FROM table_1976 WHERE "Previous Number(s)" = '61323'
SELECT "Previous Class" FROM "table_1976" WHERE "Previous Number(s)" = '61323'