Okay, so now you have a general idea of when your Ambassadeur 5000 was manufactured or assembled. There are some general characteristics of the more desirable reels. Usually, these characteristics relate to the age of the reel, with the older models being worth a bit more than the newer models. Look for that boat rash on the rims. This depends upon how you define light.
Appearance is the biggie.
Look at the handle on the reel. It is very important that the handle is the correct one. The older and more desirable reels have four screws. I'm not positive of the exact year that Abu went from four to three screws, but it might have been around 1968. The older models have an oil hole in that nut.