HDB Financial Services’ unlisted shares have been on a quiet rally. The non-banking finance arm of HDFC Bank saw its stock skyrocket nearly 31% in just the past month, riding a wave of investor optimism ahead of SEBI’s green signal for its IPO on June 3. The sharp jump in the grey market came after a relatively lukewarm six months, during which the stock barely moved 2%, according to data available on Unlistedzone. Over the past year, however, HDB shares have quietly clocked 17.5% gains, hinting at growing investor appetite ahead of its public debut.