OK here goes
For the most part model year is irrelevant It can be relevant in terms of parts sometimes but even then mostly month or VIN is the important piece of information. If you look at used values you will see that they fall more along the lines of specific models and not model year. For example you might pay more for a 1999 Iron Barrel than a 2005 depending upon accessories etc. Don't let that bother you at all. These bikes take a hit when they leave the showroom floor and
then settle into a price range that doesn't change much over time.
The boys at the factory cannot understand for the life of themselves our obsession with model year. You have to remember for 50 years when a model year changed all they did was change the calender in the parts room. I am sometimes surprised when I am researching a part to see that it's part number goes back well before they published parts books. We are still using some of those today with numbers.
For years they used an amusing system when we did have a big change such as to the ES which did change on a model year. All bikes built from whenever they started to produce those bikes (late 2001 as I remember) were stamped as Jan, 2002 models. This went on for months. It appeared as if we made as many bikes in a single months as we sold all year. They could not understand how you can make a 2002 model in 2001.
If you look at the VIN plate on your down tube3 there will be a date plate. Then look at your engine number. The last letter in the engine number is the actual month the engine was made. It is labeled A for Jan., B for Feb etc. If it doesn't math the date on the VIN the engine number is the best indication of its actual heritage.