You can use blisters to identify saffron. Real saffron is usually pale yellow when soaked in water. If you have a magnifying glass, you can see teeth, which are trumpet-shaped. In addition, you can also use iodine, which will change color when you click it.

Extended data source

Crocus sativus is mainly distributed in Europe, Mediterranean and Central Asia. It was introduced to China in Ming Dynasty, listed as medicine in Compendium of Materia Medica, and cultivated in China and Zhejiang. It is a valuable Chinese herbal medicine with strong physiological activity. Its stigma is used as medicine in Asia and Europe, which has the functions of calming, eliminating phlegm and relieving spasm, and is used to treat gastropathy, menstruation regulation, measles, fever, jaundice, hepatosplenomegaly and so on. Crocus sativus is a native species in southwest Asia, which was first cultivated by Greeks.

References:

People's Daily Online "The Secret of Saffron Vendors on the Roadside"