Activist investor Flashlight Capital Partners is publicly urging five Samsung Group affiliates, including Samsung Life Insurance and Samsung SDI, to sell their combined stake in security firm S-1 Corporation through a transparent, open auction. The affiliates collectively own 20.6% of S-1.

The affiliates rejected Flashlight’s direct offer in late August. The offer was KRW 906.6 billion, approximately $667 million.

Flashlight says the affiliates rejected its premium offer over concerns about deal certainty, rather than price. The investor argues that a competitive auction would address those concerns and maximize value for each affiliate’s shareholders.

Flashlight describes S-1 as a non-core asset for the Samsung companies. It says a sale would allow the affiliates to reinvest capital in their primary businesses.