Glad you are pleased with your gun. You mention that the CSMC Model 21 over/under is the gun Winchester designed but never produced. Not quite correct, as the CSMC gun isn't close mechanically to the Winchester design.
The CSMC gun more closely resembles it's own Inverness model, which looks remarkably similar to a number of modern O/U guns made in Italy today (such as the B. Rizzini).
A key part of the difference between the CSMC gun and the Winchester O/U design is the locking mechanism. The Winchester patent bolting mechanism locks very high on the barrel assembly, roughly abeam the center of the top barrel; the CSMC gun has the underbolt below the bottom barrel, akin to the guns I mention above. There are other significant differences as well.
Not to say that the CSMC Model 21 over/under isn't a good gun, as it certainly seems to be, it just is not the gun Winchester designed.
