A real classic:
This chest harness - cross harness - is made of sturdy cow split leather straps (2.1 to 2.3mm thick), which are connected with metal chains. In the front and back there is a large metal O-ring in the middle.
On the sides and over the shoulders, the harness can be adjusted with buckles. Two metal O-rings on the shoulders can be used for fixing.
Sorry, the shown harness briefs are not included.