If you can't get anyone to answer your question, try contacting Orvis. I have heard from others that the staff at Orvis can answer questions about older product.
You have yourself a fine reel. As of what year CFO 3, my guess that it is a 70s model. Keep in mind that I said, "guess." I have seen a few of them around from guys who still use theirs today. If I recall, the #3 model was for a 5, 6, or 7 weight (that would be a 7 wt without much backing).
If you decide to keep it, and want to have the reel serviced, I recommend Bill Archuleta of Archuleta's Reel Works in Grants Pass, Oregon. He can make parts for the reel if something breaks.