Tonbo Imaging India shares are commanding a strong grey market premium (GMP) ahead of their listing on the stock exchanges on October 23, after the defence technology company's IPO attracted heavy investor demand during the bidding period. According to InvestorGain, Tonbo Imaging shares were commanding a grey market premium of nearly 67 percent on the morning of October 22. However, the grey market premium is an unofficial indicator of investor sentiment and does not guarantee listing gains.