Only when the word "thousands of gold" is stamped can it be said to be thousands of gold. If not, the salesperson will tell you that it is not reliable. As for TX 18, it is impossible for people in the industry to know it all, especially in English. If it is common, you can know, otherwise it really depends on your personality.

Some people say that 18 should be k gold, but it shouldn't be. The current K-gold stamp should be Au750, and the previous K-gold stamp should be 18K. It can't be just 18. Please take a closer look. If there are no other marks, you should ask where you bought it.