If you have your heart set on buying an old iron barrel it might be a good buy but IMO the price is about $1500 higher than I would pay for it.
You might want to take a look at this link.
Not only does it show used Royal Enfields of all vintages but the site always seems to have interesting reading.
http://www.royalenfields.com/As you may know, the older 500cc Bullets like the iron barrel your considering are rather limited on top speed.
Although they can run faster, figure on a cruising speed in the 50's.
If you aren't trying to buy the old 1955 style engine don't rule out the new UCE, fuel injected models. Any Royal Enfield from 2010 and on has a more powerful engine capable of cruising long distances at higher speeds (65 mph).
The UCE was first sold in 2009 but I think there were also some new AVL models also sold in that year.
The AVL was an updated iron barrel which had some engine improvements designed by the Swiss.