Colorado Saddlery is a work project at the Colorado prison. Saddles were made by inmates learning a trade. I don't know if that is still true or not.
Now there's something I didn't know. My dad used to have a CS dealership while we were living in North Carolina many years ago. He bought himself and my mother a pair of CS saddles with matching tooling. Hers was a 15" roper and his was a 16" cutter. He still rides his today. They are built on synthetic trees, but are good saddles.
As for fitting your saddle to the horse, that is very important, not only for the horse's comfort, but for your safety. Some horses will eventually become hard to handle and may even learn to buck due to ill-fitting saddles. However, in my opinion, it is a lot less technical than some folks like to make it out to be.
In general, there are three basic saddle trees that will fit about 99% of all horses. The semi-Quarter Horse tree has a fork that is cut at about 88-89*, making the bars a little narrow in the gullet, to fit horses with extra tall withers or narrow build, such as some Tennessee Walkers and Thoroughbreds. The regular QH tree is normally cut at about 90*, and will fit about 90* of all horses reasonably well, particularly Quarter Horses. The full-QH tree is cut to about 91-92* and fits those horses with low withers or a broad build, short of a draft horse.
Another consideration is the length of the horse's back in relation to the length of the saddle's bars. A short-backed horse, like an Arab would likely get uncomfortable wearing a western saddle with a 17" seat and 23" bars. The tail end of the bars would be digging into his loin area as he moved. My dad has a small QH with that problem and we didn't figure out for years why he bucked at anything above a walk. Then again, I once had a Half-Arab the same size that had no problem with my 15" Simco.
You also have to pay attention to the gullet height. Roping saddles in the 70s-80s started being built with very low gullets to get the saddle closer to the horse. If you don't fit one of those right, the gullet may hit the horse's withers when you ride, and that can become a problem in a hurry. You need to have at least 2" clearance there with the saddle sitting on the horse without a pad, or you may end up with contact once it is cinched and weight is in the saddle. If you run into that, you can mitigate it somewhat by using two saddle pads, but that's not ideal.
There are oddities in horses that might make saddle fitting more difficult for some, just like there are people with physical oddities that make fitting clothes difficult, but the three main trees will fit about 99% of the horses out there. You should also be aware that the saddle that fits a three year-old ranch horse probably won't fit him when he's 20 and out to pasture. Just like people, their shape changes over time and according to their conditioning.
When looking at saddles (and it can be different for different makers), in general a tree with semi-QH bars will measure about 6" across the front, under the gullet from side-to-side about where the conchos are. It is essentially where the saddle bars meet the front of the fork. Regular QH bars will measure about 6.5" and Full QH bars about 7". And, like I said before, measurements are a little different for different tree makers. Some of the antique saddles will measure 5-5.5" in the gullet and will be cut at even narrower angles than the semi-QH tree. I attached a couple pictures to help.
Hmm. As I measured my old Hamley, it's a 15" seat, not a 14" like I always thought. How about that? You can also see that it has about a 5.25-5.5" gullet width. A bit too narrow for most modern QHs.
Well, that was a mouthful. Sorry so long-winded.