I have been using a 35" red dot artar serial #8362... in an F2 Sinar (40 inches of bellows), the results are superb but lens is huge but it's all aluminum flange (2,55 lbs total weight) and have no dust or cleaning marks when looked through light. My 2 tripods set up is a bit hard for me sometimes and I am thinking about selling it or trading in the future ( no ebay) but cant' find not much info about the $ value of such lens. I read many many threads about 19" 20"or 30 " lenses. Does anyone know what would be a fair market value of it. Your answers will be appreciated.