That looks like a good specimen. The Geoduck is very tasty, but nothing like their cousin, The Razor clam. If you didn't have to tenderize the crap out of them, they be alright. They are fun to dig up!
First on the list are these large saltwater clams that are native to the Puget Sound and have been known to live for at least 160 years. They are characterized by their long 'necks', or siphons, which can grow to over 1 meter long.