Barclays Plc investors, blindsided by the bank's $451.4 million regulatory fine for trying to rig benchmark rates, saw the stock drop 16 percent a day later. Other bank shareholders may be just as surprised. Barclays, like other lenders that help set key rates for $360 trillion in securities, has given investors scant guidance on the liability they face for alleged market manipulation. More than a dozen banks are being probed by U.S., Asian and European regulators for collusion in setting interbank lending rates. The others have mirrored Barclays on minimal disclosure.