How to distinguish the shell material of the watch?

There are a few ways to determine the shell material of a watch:

1. Check the watch specifications: The easiest way to determine the shell material of a watch is to check the manufacturer's specifications. The watch specifications will usually list the materials used for the case, including the shell material.

2. Look for markings on the case: Some watch cases will have markings or engravings indicating the material used for the shell. For example, a watch made with a stainless steel shell may have "Stainless Steel" or "SS" engraved on the back of the case.

3. Perform a magnet test: If the watch case is made of a non-ferrous metal like titanium, it will not be attracted to a magnet. On the other hand, if the watch case is made of a ferrous metal like stainless steel, it will be attracted to a magnet.

4. Check the weight: Different materials have different densities and therefore different weights. For example, a watch made with a titanium shell will generally be lighter than a watch made with a stainless steel shell.

5. Perform a scratch test: Different materials have different levels of hardness and will scratch differently. For example, a watch made with a sapphire crystal shell will be much harder to scratch than a watch made with a mineral crystal shell. However, it's important to note that scratching the watch case can damage it, so this test should be performed with caution.