Fake. Only chance of reality is an altered date 1874. Or if you mean an 1881 proof. But a 1871 would be a seated dollar
There are pattern 1871 trade dollars, but a real one of those would be highly unusual to run across. On the other hand there are literally thousands of Chinese fake 1871 pattern trade dollars.
I have someone trying to sell me an 1871 s trade dollar. It looks good but the date makes me worry. How can I tell if real?