This is 2 silk first day covers from China in 1991 numbered T164.
They feature Chengde Mountain Resort and are slightly right stamped.
On the back of the covers there is a description of the creation of the stamps. The designer of the cover and cancellation is Liu Dun.
The smaller cover measure 9" by 4.75" and the larger covers each measures 7.25" by 4.25".
These first day covers come in excellent mint condition with no marring or discoloration.