When purchasing a used M11, here are a few buying tips. Always make sure the serial number begins with a V. Any other letter indicates you are purchasing the Old Style autoclave that will only cause you grief. The manufacturer no longer has parts or support for this older machine. You should always ask for both the serial number and for a picture of the sterilizer. If the serial number does not begin with the letter, V stay away from this autoclave. Also, the display should always be green, not red. Once you establish it is a V series serial number another important thing to know is this. Has the mother board ever been replaced? There was a point of failure on the fuse housing causing most of these autoclaves to fail. Midmark recognized the issue and updated the control boards on all their machines. But unfortunately, there were hundreds of these autoclaves still sold with the faulty board. The only way to know is to take the cover off the autoclave and find out if the control board has a green back. All the updated boards have a red back not green.