Note the outside edge of the coin? 1. If it extends beyond the circle caused by the collar, then you know the coin is altered. 2. If the rim is disturbed and moved out of its correct location, then the coin was altered. The collar and rim is formed during the strike. Sure you can have examples struck with out the collar, but the edge would not be contained and the rim would not be formed: https://imgs.inkfrog.com/pix/coop49..._COOP__1.jpg
So if there is not rim, it might be a mint error. If the coins edge is not round, it is probably not a mint error. So know what things to look for on a coin to see if the coin was altered, then you will know what the answer is.