Business Notes SOVIET UNION

In typical Soviet fashion, perestroika took another lurching step forward last week. TASS, the government news agency, announced formation of a Moscow Stock Exchange, the first since 1917. The new exchange already has 187 prospective companies and banks. Soviet securities will be represented overseas by international brokerage firms. And Moscow's Big Board plans to open offices in other world financial capitals, like Tokyo and New York.

A detail still to be ironed out: building the exchange. A site has been chosen, but officials don't know when construction will be done, what it will look like or when trading will begin. Talk about speculative.