Ask to see the specs!
I had exactly this filter and took world-class images and animations with it. I was amazed at the details of the chromosphere I was getting with a 5-inch refractor. However, whether you buy used or new I highly recommend that you ask to see the specs rather than spending thousands of dollars and being surprised. Daystar filters can be spectacular or average, because their quality control is either excellent or average. The professional version of the Quantum is supposed to be checked more carefully, but my experience is, don't take a chance.