Probably shouldn't be this excited for a dirty old sleeping bag, but I am. Will be adding this Class 5 Mountaineering Equipage(!) goose down mummy bag to my camping kit. 5 bucks. Check out that huge zipper! Picked up an even older goose down bag last weekend at an estate sale for free, no tags that I have discovered though.
Score! Class 5 is one of my favorite vintage makers. I've found jackets, vests and packs but never a sleeping bag, Great find! Like Fueco said, definitely toss it in the wash and then in the dryer with some tennis balls.