The K-53 in the picture is for display only and is not for sale.
This is a Mosin Nagant gun sling produced by CHICOM for Vietnam in the 1970s.
 During the Vietnam War, CHICOM provided a large number of K-53 rifles to the Viet Cong. 
K-53 is the Chinese authorized production model of Mosin Nagant M-1944.
This strap has a Chinese stamp, but the content is a Type 56 SMG sling. 
Perhaps it was stamped incorrectly during production, or perhaps in order to provide it to Vietnam urgently, CHICOM modified the Type 56 SMG sling in stock.
This is an interesting phenomenon. As we all know, the Chinese Communist Party has not produced K-53 since the 1960s.
The product is original.

Width: 2.9CM
Longest: 123CM
Shortest: 72CM