Added 3 more images to
http://imgur.com/a/buHMz
Dad somehow cross-referenced some material and thought Parker was involved. Ya'll are starting to convince me though
It clearly has E marked, but I also see an F on the flat. Dad also was confused with an excerpt from the Double Shotgun book ya'll referenced, because it states the E grades didn't have gold or silver in-lays. Maybe it's an F grade?
This is fun, thank ya'll for the help so far!