Helmets fitted with masklike visors were a popular German and Austrian fashion about 1510 to 1540. With their visors forged and embossed as humorous or grotesque human masks, such helmets were often worn in tournaments held during the exuberant pre-Lenten (Shrovetide) festivals, celebrations somewhat akin to the modern Mardi Gras. Substitute visors of more conventional type were often provided for everyday use.
Interestingly, the postulated 1515 date for this helmet would make it contemporary with the "horned helmet" previously posted at Neatorama.
Link, via Titam et le Sirop d'Erable. Photo credit Metropolitan Museum of Art.