Sterling Silver
Year (and years) ago, I commissioned a guy in Sydney, Australia, to make me a sterling cock ring. At the time, you couldn't find them at all. We discussed how to measure properly (via email) and a couple of weeks later, I received a package in the mail. I also ordered one for my husband which we proudly wore to pool parties and such.
We later started an online business making custom cock rings in sterling silver. Because of a job relocation, we shut down the business, but in the 11 months we had our site up, advertisements in Genre and Advocate brought us many customers.
I wear my ring pretty much 24/7. The secret is getting the perfect fit - tight enough to avoid falling off when I'm soft and large enough to accommodate my erection.
I used to love sitting in a board meeting or high level engagement just knowing my package was encircled in precious metal. ;)