Mumbai, Sept. 24 -- The National Stock Exchange (NSE) tests investor appetite in a landmark public debut on Thursday, concluding a decade-long journey to the stock market. The NSE stock is likely to make a modest debut despite strong institutional participation, with more than 100 qualified institutional buyers (QIBs), excluding anchor investors, bidding for Rs.4,498 crore worth of shares, according to three people familiar with the share sale allotments. Institutional participation has been strong, while retail investor bidding has been relatively subdued. The unofficial grey market premium (GMP) fell from around 21% at the start of bidding on 17 September to 2% at the close of bidding on 21 September, amid concerns over the valuation. "Th...