(Crain's) — Russian investor and Internet entrepreneur Yuri Milner turned plenty of heads a year ago when he led a $135-million investment in Chicago-based Groupon Inc.

It looks like a shrewd investment now. His 4.6% stake in Groupon is worth $695 million, if even the low end of the rumored $15-billion-to-$20-billion valuation for a Groupon IPO is accurate.

Mr. Milner’s stake in Groupon was disclosed in the annual report released Tuesday by his Moscow-based company, Mail.ru, formerly known as Digital Sky Technologies, which went public last year.

Mail.ru operates two of the three largest Russian websites. He has a track record of taking later-stage investments in hot U.S. Internet companies, with stakes in Facebook Inc. and Web-gaming site Zynga Gaming Network Inc.