Potentially fine. Some thoughts for consideration:
Separately, I use these abbreviations as part of image filing for the VPID.
The requirement there is similar - unique, clear - but with a preference for clarity/memory/understandability over brevity.
Therefore, while I use most abbreviations as-is per this list, I often use a pre-pended "q" for the quinta-branded releases.
In this case "qC" being possible; not already used, and different from any other C.
Similarly I have used qLR (or qdLR, I haven't been rigid to date since brevity less an issue for me) for Quinta de La Rosa. LR is fine currently, but there will likely be more conflict between quinta brands and other existing abbreviations, and the simple "q" prefix could be used to reduce the issue.
n.b. no actual objection to Ct per previous/current method, but seemed like a good time to raise this.