Examine the line under a high power lens and apply the tip of a toothpick to it. If the metal flexes, then it's a linear bubble in the plating. If it doesn't flex then it's most likely a die gouge or a linear die dent.
Looked on the reverse as you stated. Well, if I look hard under a microscope, I can see that there is a tiny bit of doubling on the "O". Bummer. However, I just noticed that mine is an '84, not an '83 as pictured. The spear on my Lincoln starts just under the "G" but still spears him right through the head. 2 yrs with the same thing? Hmmm...