Tucked away in historic Florence, L'Antico Setificio Fiorentino was founded in 1786
The painting, only recently rediscovered, was the last da Vinci left in private hands
The painting stands as the first discovery of a Da Vinci painting since 1909
The dreamily sensual sketch of Saint Sebastian is thought to be worth around 15 million euros
Infrared technology was used to examine the painting