I would consider cleaning it, non abrasive, very gentle soap on the decal areas, dry completely, might try kerosene at the hub & headset areas only to remove dried grease. Problem with taking it apart is to keep it from getting damaged, removing the cotters without damaging them and or leaving marks will be a challenge, not impossible but risky, as would be removing the headset and Bottom bracket. I would vote a good cleaning, more like a washing, then sell it. These are very rare in this country, which is good, but bad as they fly below the radar. If I had fewer projects I would be interested, I do have a 58.5cm 531 DB Gazelle though...