How do you know if it's counterfeit or not?

its actually more half art and half science question

depending on the item, some counterfeit is easier to spot, some is harder

do you have any item in mind? and perhaps take a photo so we can judget

Explanation:

hashbrowns you can make these with those preperation methods

the answer of "what has three legs but never walks" is a yard stick. this answer can be found at