GORGEOUS ring but confused on mark!

Ring stamped 14K CDC. In looking up CDC, I keep coming back to a store/company called Central Diamond Center here in TX that started in 1989 unless someone else knows of 'another' CDC. The most puzzling thing is this was part of my grandmother's jewelry and she had passed years before that. Another thing, she lived in Florida and not TX, not that they couldn't have bought it from TX, but they never understood or had computers so there was no chance of an online purchase. I looked up the researching costume jewelry site and do not find CDC as a known mark so I guess I have to accept that somehow this mysterious ring got into my grandmother's oldest / older ring boxes after she passed? My grandfather passed a few years after that. Wow...just stumped here. I presume that if this ring is from the central diamond store, that the quality of the diamonds is not very high...