Here are lamp chains and lamp chain for different weight classes.
The lamp chains are made of iron that is plated or varnished.
Here's how we checked the strength:
Pulling until the links begin to widen, then the load is lowered so that the links return to their original shape. Locking and reading of weight. Can we exceed the values we specify here ?: Yes, you can - the roughest chain we have given 12kg can handle more than 20kg. At 14kg the links have opened 1/4 mm.