CTR stand for "Choose the Right". It used to be (and still is, I think) the name of one of the church classes for young kids, around 8 years old. When I was that age, it was the custom to present each kid in the class with a ring that had "CTR" written on a green shield. The purpose was for the kid to always be reminded to make the right choices.

Anyway, sometime between that time and the time I went to college, some marketing genius decided that the CTR logo was pretty cool, and that adults would pay for the privilege of wearing it as well as the kids. So, they started making (and still do, I believe) adult CTR rings (real jewelry), out of gold and silver.