Nipple shields

I was taking an on-line quiz and came to an image of antique nipple shields (2nd photo) from the Wellcome Library. The caption did not answer my questions about why and how early such a thing was used, so I'm sharing what I found out:

Nipple shields have been - and still are - used by women to facilitate breast-feeding their babies. They are placed over the aureola to 1) help a small or weak baby keep a grip, 2) augment a mother who has flat or inverted nipples, or 3) habituate a baby to the breast after it has been bottle-fed, all of which are lumped under "latching problems." It seems that in the past, they have also been used to protect sore nipples and removed to nurse, as described in 1649:
"If when the child's teeth begin to grow, hee chance to bite the nipple of the nurse's breast, there will bee an ulcer verie contumacious and hard to bee cured, becaus that the sucking of the childe and the rubbing of the clothes do keep it alwaies raw..."

Today, nipple shields are formed from flexible silicone. But in the past, they have been made out of materials including glass, wood, ivory, India rubber, leather, and solid silver (1st photo). They were readily available in the 19th and early 20th c. and sold with soft and pliable teats made of animal skin. The August 1922 issue of Hospital Management references a popular lead model designed by British Dr. Wansborough in 1842 (and advertised here in 1862), but prefers the aluminum design by Dr. Charles Edward Ziegler of Pittsburgh, Pennsylvania. By 1949, the dangers to the baby of lead-poisoning were known, but by then lead nipple shields were already considered antiques.