The rectangular area outlined by 1-2-3-4 ?
Looks to me like it's a rectangular washer under the bolt head. Not translucent but that color, probably metal, and flat against the mounting steel.
If that's the case, then the sign must be plastic as they wouldn't need a retainer that size to hold a metal sign.
That means the Farm Bureau, or their agent, lied....and probably killed Kenny, too.
