I was cruising EBAY, looking for a Polaroid back for my 4x5 cameras; I wanted to try some image transfers. I noticed that the vintage #500 Pola back went for about 1/3rd of the price of the current 4x5 Pola back. The info on the auction stated that it worked with all modern Polaroid 4x5 sheet films. I bid $24 and ended up winning it. After I bid I searched for info on the #500, and was horrified to find that more than half of the sites and posts I could find about it stated that it was absolutely incompatable with modern Polaroid sheet films. It arrived in the mail and I bought some #59 Polaroid film. I've been using it for the last three weeks and I'm glad to report that it works fine. Apparently some people were having problems with pulling the paper dark-slide all the way out, and not being able to re-insert it. The modern Pola back hads a catch that stops you from doing this. The film comes with a circle and crosshairs sort of registration symbol on the lens side of the film. Pull the film out until this is visible, and that is exactly the right distance.