Leather mask added to helmet to protect the face. At first many teams tried it. But it was scratchy, blocked their vision and hot! So it faded away quickly. Has become the "collector's Eldorado" to find . RARE RARE RARE Some teams continued to use them for their injured players right into the late 30s.
Very few have survived,. Very rare. Last original we saw in excellent condition sold for $10,000 !!