The two kinds of Zheng are of the same grade, and D is unsigned and signed. The so-called signature is the guzheng of the same grade recognized by the director of Dunhuang Factory. There is a note on Zheng's body that says "producer Xu". 694 is a mid-range Zheng, and the factory is about 1700. There is no problem for beginners. If the level is high, such as level 8 and level 9, it will be a bit troublesome to use. You need a better Zheng. Signed ones should be better than unsigned ones. 2300 can buy signatures online, and you can also buy signatures if the music store is cheap. Cut 600 yuan first, the price of guzheng is quite high. There are nine levels of Dunhuang guzheng: 699, 689, 696 and 694. 694D (signature), 694KK, 695, competition signature Zheng, limited edition Zheng. 694KK and 695 are more advanced, and the first few of the elementary and intermediate ones will do. 696 covered with mahogany, the tone is better. The first few are imitation mahogany. Beginners can also learn 696. There are many fake pipa in Dunhuang. Looking for the trademark "Fairy Holding Pipa", Shanghai No.1 National Musical Instrument Factory.