The Sensex at the Bombay Stock Exchange closed with a modest gain of 41 points, or 0.3 percent, at 16,658, today, on buying interest at lower levels, and amid a somewhat better trend in the overseas markets. The Nifty at the National Stock Exchange rose 13 points, or 0.3 percent, to close at the 5,000 level. Stock markets in Japan, China, Hong Kong, Singapore and South Korea ended mixed.