One thing Fred told me when I spoke with him. He said no matter what condition you find one or buy one in that's used, It has probably lost some of the fluid inside sometime during its use. Then they won't last or enguage well.
Mine looked alright initially, but I figured I didn't want to end up sending it out later. So last Feb. I sent it to him. I can't wait to get it. I'll post a pic of it when it arrives.