If selling a company, never open the bidding, as that reveals your cards.

FORBES: Making a Killing

But a battle could be on the cards, since Harmony Gold is thought to be bidding for some of the same mines, although it has yet to say more than that it is in talks with a third party.

BBC: Business crosses the line in South Africa

"The bidding procedures are designed to allow bidders to give us their best offers without fear of showing their cards to competitors, " said the firm's chief intellectual property officer, Timothy Lynch.

BBC: Kodak printer