Clackamas Oregon is where Kimber started out ... the guns made in their little ship in Clackamas are considered by many to be their best (in part because they are basically "Series 70" 1911s and not "Series 80" like the Series 2 guns ... with their Schwartz style firing pin safety that apparently ruins the trigger pull).
I think its also because Kimber changed hands a couple times before it moved to Yonkers NY (where it is now) and the focus of the company was building top notch custom 1911s in Clackamas and now their focus is mass production in NY.
Now I may be wrong, but I think Kimber of Yonkers started out making Series 1 guns (well actually they were never called that until the Series 2 guns came out). So just because its not a Series 2 doesn't mean for sure its a Clackamas.
[EDIT] Kimber moved from Oregon to New York in 1997, the Series 2 came out in 2001.
EDIT
Did some googling.
Clackamas Kimbers will be stamped on the right side of the frame "KIMBER, CLACKAMAS OR USA" and later ones will be stamped "KIMBER YONKERS NY USA"

