SWISS NATIONAL BANK SAYS IT BOUGHT DOLLARS The Swiss National Bank bought dollars against yen today, a spokesman for the bank said. He declined to say how many dollars the bank bought or when precisely it intervened. Swiss foreign exchange dealers described the National Bank's purchases as modest, perhaps amounting to no more than 20 or 30 mln dlrs. The Bank of France, which was reported buying dollars against the yen in Paris, had made inquiries with Swiss banks as well, and the Bundesbank had also intervened. Bank of Japan dollar purchases today were perhaps 1.2 to 1.5 billion dlrs. Dealers said this tended to confirm the market's impression that major industrial countries had agreed at the Paris meeting on an effective floor for the dollar of 148 yen, and the market seemed ready to test it. Commercial clients were also selling dollars against the yen as the end of the Japanese fiscal year on March 31 drew closer. Today's dealings in spot currencies are booked for March 31. One dealer said he had the feeling Japanese companies had been asked by the Bank of Japan not to sell dollars at this point, but some, while sticking to the letter of that request, were offering dollars forward today, rather than lose out if the dollar fell further. The run on the dollar against the yen came in a market thinned by the absence of many dealers for a Forex Club meeting in Hamburg. Trading was, in fact, rather light against currencies other than the yen, the dollar holding little changed through the day. The market now expected the U.S. Federal Reserve to intervene in support of the dollar. "But they will probably do it only half-heartedly, so I don't think it will matter too much on rates," one dealer said.