Yeah Balls were always spec watches shopping around to various American manufacturers.
There's actually a lot of discussion around this.
Ball watches are generally readily identifiable as to the company that made them by the plate layout and a few other features, although you'd occasionally see some Ball-specific features on a watch. Generally the Official Railroad Standard watches had a distinctive circular damaskeen pattern.
They did, at least at one time, do the final adjustment and timing in-house rather than taking what was delivered. Jeff Hess, who is president of the current Ball USA, at one point had unearthed correspondence from I think Waltham acknowledging Ball as a manufacturer. That comes with some caveats, though, as it was from a time when Waltham was headed downhill and they were probably trying to win brownie points. At that point, Hamilton was the primary supplier to Ball. There were also some interesting things too, like a particular type of hand fitted to Illinois Ball watches.
This is one of my favorites, and interestingly enough it's not actually marked "Ball" anywhere on the watch. These were some of the earliest Ball watches, and carry private labels for various Ball jewelry stores. This particular one is still operating. I'd actually been shopping for one of these for quite a long time. I'm not a Ball collector, but it's a key piece in another part of my collection. I'd watch a couple come up for sale, and had bid on a few. One at Bonhams fell with a cheap hammer price and I did bid on it, but it had the wrong dial(probably an impossible fix, or nearly so) and didn't make reserve at $850(I dropped out at $800). I pushed another on Ebay up to $2500, but wasn't comfortable going higher(honestly higher than I should have, but that's an auction for you) because it had a few condition issues that would have bugged me. That one stopped at $2800.
Finally, a couple of years ago, I was at the Cincinnati show and a dealer from up around Cleveland called me down and said he had something I might like. We came to a deal on it, and I walked away with a smile on my face. It was between those two numbers I mentioned above, but closer to the lower one, and nicer than the higher priced one.
BTW, to the original question on becoming an "expert"
I've been knee-deep in American pocket watches for over 10 years now, which is no time compared to what a lot of folks have done. I know a lot more than I knew 10 years ago, and a lot of that knowledge has come from published sources, observing watches(including a lot of holding them in my hands and looking) and more than anything talking to and learning from other folks, then putting the "big picture" together as best as I can from all of those. There are a few very narrow fields of American watches-in particular minor variants of Waltham 1883 model Crescent Sts and also cataloging of Kentucky Private Labels, where I may be able to claim to know at least as much as anyone living on those subjects, but those are incredibly narrow fields.