I will look up the serial number in Thiele's book after I return home, if no one beats me to it. Have you ever unscrewed the front of the lens to check if the rear lens group is stamped with the last six digits of the serial number? This is probably the best single indication of the lens origin. The engraving of the beauty ring and lens barrel looks a bit odd, but this is not definative, of course. One good sign is that the lens has the two screws on the focus ring characteristic of war-time and immediate post-war CZJ lenses (one is used to hold the focus ring in place, the other limits travel of the aperture/iris) - the ZK lenses also have these two screws. One thing that does stand out is the silver sleeve around the rear lens element; this is usually black in color. The silver sleeve is usually found on what Brian Sweeney calls a "transition" lens.
Maybe Brian will check in later.
I see that buzzardkid has already provided serial numbers. That was quick!