1. The original crusader soap is black while the fake one may be blue or ash.

2. The original soap has a very hard texture and doesn’t dissolve easily in water but the fake can be compressed when pressed between the hands and easily melts away

3. Even as the original crusader-medicated soap is black, the lather it produces is white. For the fake soap, you might see green, blue, or any other colour.

See the full list here

https://eucarlcosmetics.com/how-to-know-original-crusader-soap/