How to identify stainless steel which is not contained the nickel?

Now there are a lot of cookware on the market, although signs are written in stainless steel, but actually they are "stainless iron" products. So, how to identify stainless steel  and "stainless iron" products?

Recognition from the tag: Many stainless steel products have steel seal which is stamped in the surface of products, model of words such as 13-0 ,18-8, and so on, in front of the number of short-term represent chromium content of products, short-term behind the numbers indicate the amount of nickel content of products. Such as 13-0, it is only as non-chromium nickel, commonly known as "Stainless Iron "; and 18-8 that products contains nickel chromium, this is stainless steel.

Recognition from the sound: Knocked the stainless steel or "stainless iron" products can also be used as a method to judge.

Use permanent magnet:  real stainless steel will not be attracted to magnet, "stainless iron" can be attracted to a magnet.

Although the "stainless iron" and stainless steel are different in their properties, but in terms of its corrosion resistance ability, both of two are better than wrought iron and cast iron cookware.