If there are no o rings at all, it's first generation:
http://www.smokingmetal.co.uk/pipe.php?page=262
Personally, I like the way the Falcon smokes more than either the Kirsten or the Viking. All provide cool, dry smokes, but the Viking tends to gurgle after a while, and the Kirsten has a less free draw than the Falcon. Additionally, the Kirsten tends to 'overkill' with its mechanism, thereby enabling less tobacco taste to reach one's mouth. My experience with over 30 metal-framed pipes is that the Falcon and the Koolsmoke provide the most pleasurable all around smokes.