Cristoforo De Amicis (1902-1987) - Nudo di donna

Good morning, I am sending images of this artwork "Nudo di Cristoforo de Amicis 63"; I don’t know what technique was used, but they exist in various archives.
Cristoforo de Amicis was born in Alessandria 1092 - 1987 Milan. He studied at the Albertina Academy of Turin, then moved to the Brera Academy, and later obtained the chair of painting at the Brera Academy. Truly a great painter...