There was one more layer of symbolism to the ring that was mentioned in the super-secret ring ceremony (which is well-documented on wikipedia). New rings have rough edges due to the bevelled decoration; over time it smooths out, symbolizing one's maturing as a professional.

I heard a friend-of-a-friend story that described a senior engineer who lost his ring and had to get a replacement. He complained that he "felt like a kid" with his fresh ring and was apparently found in the metal shop later grinding down the edges.