How to know the stainless steel wire rope is 304 or 316?

Since we know that we can't judge 304 and 316 Stainless Steel Cable by using magnet, because 304 and 316 are slight magnetic too, what else should we do?
Here are our advice:
1. When buy ropes, chose a reliable and professional supplier.

2. Use a spectrometer to detect the ropes, the spectrometer will show the chemical elements result, as below picture showing. Although the detection result of the spectrometer is not very accurate and has some deviations, it is enough for us to simply judge the material.

3. Find a professional testing company. The testing company will show you the chemical elements in details, and their result is trustable. We recommend using this method for detection.