I sold my Polaroid 405 backs when Fuji made their cuts, figuring it would be the last chance to get any money for them. Not surprising that new Polaroid can't do it, unless they want to buy Fuji's production line. (tangentially, I had an RB-67 for a while too. They're great, but I ended up trading it for a Hasselblad, because it's half the size)
