The brand of Gucci comes from Italy. However the Gucci sunglasses can be made in several countries, such as China, America and so on. With the globalization of economy, many companies have the branch ones in other countries because of the cost consideration. Thus, the Gucci sunglasses owning the mark of made in China can be the real ones. If you don't know whether it is true, you can go to their exclusive store to ask the clients.
As a matter of fact, Gucci sunglasses is a notable Italian brand which is famous for its luxury goods and high quality merchandise. Actually, it is also one of the most expensive sunglasses in the world. As it is located in Italy, so it is generally made in Italy. And as to your second question, how to tell its authenticity right? I have some advice for you here. First, you should be sure that you bought it from a large shopping mall or some places like that. Second, make contact with its after sales service to see if your sunglasses are real. Hope you find it useful.