If you think you have a coin with a clip planchet take an identical coin and lay it up to the clip. If it fits, you've got a clip, if not, no you don't.
This is a good rule of thumb, and I like it. There are also other factor to take into account. to be sure it is a genuine clip. There are also straight clips from the edge of the planchet stock strip. There is a ragged edge and Blakesley Effect. Read here.http://www.error-ref.com/blanking-and-cutting-errors/.