More than a month after Russia announced one of its biggest privatizations since the 1990s, selling a 19.5 percent stake in its giant oil company Rosneft, it still isn't possible to determine from public records the full identities of those who bought it.

The stake was sold for €10.2 billion to a Singapore investment vehicle that Rosneft said was a 50/50 joint venture between Qatar and the Swiss oil trading firm Glencore.

Unveiling the deal at a televised meeting with Rosneft's boss Igor Sechin on Dec. 7, President Vladimir Putin called it a sign of international faith in Russia, despite U.S. and EU financial sanctions on Russian firms including Rosneft.