I think that T stands for thousands. not 100% sure, as I scanned the page- but with all the info on it- I'm in overload and will have to read it again. I does look like the page is more informational about someone shopping for a good ring, but the info seems pretty interesting non the less..hopefully I'm not breaking rules posting links to info (on a sales related website- as I'm not trying to sell anyone anything!) anyhow again, good find 18K gold!!! rock on.