It appears to be the hood emblem from a 1959 El Camino and Impala equipped with a 348:
Hard to believe anybody would take the trouble to mask around that, unless they just painted over the emblem!
This emblem actually seems to make a very nice fit to the hood. I'm surprised there haven't been more added to these trucks, but perhaps due to the rarity of 348/59 Chevys & El Caminos there aren't many to be found.