JAKARTA (Aug. 17)—The burgeoning strength of the Indonesian rupiahùwhich went from 12,000 to the U.S. dollar at the beginning of the month to 8,600 nowùis the main reason for an uptick in the price of Standard Indonesian Rubber 20, experts said. "It's not a substantial rise, but if you have to credit one factor for it, it´s' the currency," said Kip Tobin, president of Centrotrade Rubber U.S.A. in Akron and of the Rubber Trade Association of North America. SIR 20 rose from 28 1/4 cents per pound Aug. 1 to 29 1/4 cents now, delivered to the U.S. This gives its near-parity with the slightly higher-priced Standard Malaysian Rubber 20 (30 cents per pound) and Standard Thai Rubber 20 (30 1/8 cents). The supply and demand situation for natural rubber, however, has not changed, according to Tobin. "There are still good quantities of rubber available for shipment in the Far East, and buying interest is muted from all consumers," he said.