1964 LMC Double Mint Clip

Nice find! On clip errors, you have what's called the Blakesley effect where side opposite the clip, will have a flattened rim appearance to it. On your coin, it is shown best on the reverse directly across from the large curved clip, and next to the designers initials (FG). See how the rim is flattened slightly. This is a sign of a genuine clip error. Also, in this case, a LMC, another cent should fit in the large clip area fairly closely to the cents size.