This is what Wikipedia says:
“Room 39 (officially Central Committee Bureau 39 of the Korean Workers’ Party, also referred to as Bureau 39, Division 39, or Office 39) is a secretive North Korean party organization that seeks ways to maintain the foreign currency slush fund for the country’s leaders, initially Kim Il-sung, then, in progression, Kim Jong-il and Kim Jong-un.
The organization is estimated to bring in between $500 million and $1 billion per year or more and may be involved in illegal activities, such as counterfeiting $100 bills (see Superdollar), producing controlled substances (including the synthesis of methamphetamine and the conversion of morphine-containing opium into pure opiates like heroin), and international insurance fraud.
Although the seclusion of the North Korean state makes it difficult to evaluate this kind of information, many claim that Room 39 is critical to Kim Jong-un’s continued power, enabling him to buy political support and help fund North Korea’s nuclear weapons program.
Room 39 is believed to be located inside a ruling Workers’ Party building in Pyongyang, not far from one of the North Korean leader’s residences.”
And, in the immortal words of that endearing radio personality, Paul Harvey, “and now you know the rest of the story.”
Of course, the real story is here.