I'm helping a relative (the widow, kind of) with an estate sale, most good stuff are already gone, but I found this enigmatic lens in a lens bubble, serial number is just above #890000, can't remember exactly. It's in pristine condition, and I have the bubble and special cap. Question is, how do I unload it? There was one sold on the bay for $600, and another for $207.5. Are there any other ways of selling it to a collector? The apug ads seems to cater more to users, and this is both rare and kind of hard to use.