What material were the first legal condoms in the US made out of?

Explanation

Womanizer Giacomo Casanova (1725-1798) is said to have used linen condoms. The first legal condoms in the US were made out of vulcanized rubber and date back to the 1870s. They were both very expensive and very thick, however, as they were meant to be reused. Today, a normal condom is only 0.07 mm, but can be as thin as 0.05 mm. As a comparison, clingfilm is almost 6 times as thick. During WW2, American GIs used condoms to protect the tips of their rifles when they swam towards the cost.