Does this mean the gains made were artificial?

It appears the Naira is defying the Central Bank of Nigeria's intervention to make it stronger.

The Naira on Tuesday eased 1.2% against the dollar on the black market on Tuesday, weakening to 410 Naira to the dollar.

On Monday, the apex bank auctioned $100 million in forwards to be settled between one week and 30 days' time, as against 60-day contracts it had written previously.

But the naira was quoted at 410 per dollar on the black market on Tuesday, weaker than the 405 it closed on Monday.

The central bank, opposed to a free naira float, has been selling the U.S. currency on the official currency market to try to narrow the spread with the black-market rate after the black-market rate hit a record high of 520 in February.