Many of the silver-clad halves (1965-1970) show a line along the edge caused by the different color or reflectivity of the center 20% silver alloy compared to the outer 80% silver alloy. However, some have a uniform bright silver edge with no visible lines. A few worn or dirty examples show a reddish edge tint that makes them look like a copper-nickel clad coin. All these are "normal" variations.
The ones to watch out for are the 1965 coins with 12.5 gram weight. Those would be rare errors struck on leftover 90% silver planchets and are worth a lot. I don't know anyone who ever found one but they do exist.