That is way too old to even hazard a guess. Unlikely hen unless it was from last year and even then the heat and rain of summer completely wipes out even the cores I leave around the bushes at my apartment after cleaning.
Frank, all mushrooms are edible...at least once. By large shelf mushrooms you could be speaking of anything from Artist Conk or ganoderma to Dryad's Saddle, to a myriad of others. If possible, clear photos of the top, bottom of cap if it is capped, stem and description of trees nearby will help. I will do my best but as I post in many forums never rely on and ID from a photo on the internet when your liver and kidneys may fail in 7 days with deadly look a likes to common edibles. There is one fall/winter/spring mushroom I won't even post as another that grows on dead fall, the deadly gallerina is SOOO close in appearance until you are accustomed to identifying the \"January mushroom\" velvet foot. Thanks for everyone's interest happy root gathering, growing, buying and selling. I am thinking of marketing on a small scale ground dehydrated mushrooms which will cut shipping costs and really add flavor to many dishes. As this draws near with the permission of the owner, I will offer a few free sample packs of powders of various edible/medicinal fungi if anyone is interested?