This is the Excellent Cll .21 roundball. It difference from the Cll K is the loading port. It is also newer than my Cll K .177 and .21. Being made in the late fifties.
Professor,
Looks like they went to a simpler, less expensive loading port in later years. Looking at the pictures, one reason for the heavy-spring pressure thumb button seems to be to hold the loading port tightly to the breech. Effective, as demonstrated by accuracy, but hard on the thumb. Curious to know how snugly roundball ammo fits in breech now that you can load directly. Thanks for interesting post.
WM