Also, at the risk of confusing things further, let me point out that the model numbers and model names don't always refer to the same thing.
For example, you wrote:
If it was made in 1952, it is not a Model 18. It is simply a .22 Combat Masterpiece. It is what would become the Model 18 in 1958, but it is not a Model number anything. Some refer to them as the "pre model 18" but I personally dislike this type of reference. S&W gave them names, that's what the catalog called them and I think that is what we should call them. After the directive of September, 1957, things changed. Model numbers were added, although the names remained. So after 1957, it is proper to refer to a gun as, for instance, a Model 15 Combat Masterpiece, or a Model 14 K-38 Masterpiece. The Instructions for Use paper that used to ship with these guns used this terminology, reflecting the position of the company. The guns continued to have names, but also carried model numbers.
I hope this helps your understanding of the guns you are now interested in.
Jack