TIL (today i learned) that engineers wear an iron ring, an take an oath, which concludes

As an engineer, I shall participate in none but honest enterprises. When needed, my skill and knowledge shall be given without reservation for the public good. In the performance of duty, and in fidelity to my profession, I shall give the utmost.

These days it's usuaslly stainless steel.
https://en.wikipedia.org/wiki/Engineer%27s_Ring

Stainless steel was invented in indiana by the haynes corp, that my roommate's grandfather worked for.