If it's just for display and not too dirty, I would leave it. If you do decide to wash it, I would disolve a gentle cleaner like retro clean or similar in a bath tub half full of cool/warm water. I would hand agitate it a little and let the water drain out. I would refill with rinse water and hand agitate gently again. Let the rinse water drain and let the quilt drain until it isn't too heavy to lift out. Depending on how fragile it looks, you could bring it to the washer and spin some more of the water out if you think it can stand the spin cycle. I would then lay it on a flat white sheet to dry (outside in spring). If you put it in the dryer, you might have the cotton batt shift or the stitching pull out in the tumbling.