The Museo del Prado in Madrid has acquired a rare early Renaissance triptych once part of the Álvarez Fisa Collection for €4 million, El Confidencial reports.

Not much is known about the artist behind the Triptych of the Birth of Jesus, which depicts the birth and adoration of Christ in lush colors divided by ornate gilded frames. It is widely thought to have been painted by an unidentified artist from Northern Europe—dubbed “the Master of the Zarzoso Triptych”—who painted in the Flemish style.

The triptych was painted in the province of Castilla, Spain, around 1450 and hung in the Zarzoso nunnery in Salamanca for centuries, maintaining an outstanding level of conservation.

Since 2013, it has been displayed at the the Prado museum as part of a showcase gathering 18 highlights from the collection of businessman José Álvarez Fisa, a long-standing member of the Prado’s Royal Board of Trustees, who died that same year.

Out of this group, 12 works were donated, while six, the triptych among them, were temporary loans. But the museum expressed interest in purchasing the anonymous masterpiece early on, and it has now bankrolled the operation— and without any governmental subvention, an unusual occurrence in Spain.

According to El Confidencial, the sum will be paid to the heirs of Álvarez Fisa in yearly, interest-free installments over the next four years. The extra cash found in a Swiss bank last year, bequeathed to the museum by a discrete private donor, seems to have already been put to good use (see Museo del Prado Finds Over €1 Million in Swiss Bank Account).