Although Hamilton was the premier American watch brand, not all watches were made for the US market. Some models were never produced for the US market... for example, solid rose gold Ventura models were produced for export only. They are few and far between though and command a healthy premium when they do come up for sale.
It's not unusual to come across models, especially from the 1960s and later, that are hard to identify and not shown in the Hamilton catalogs. Usually these models will also have model numbers on the case back that will provide a clue.
I recently received a watch that I got midway through before I realized it would be a good blog post.
It's a Hamilton Estoril of some sort. I thought it might be from the 1970s, however, with a little digging I realized it might be from the mid 1960's.
My project watch originally made it's way to Hamilton for repair but they weren't willing to fix it (or it would cost too much). That's not surprising. I suspect if you brought a 1965 Mustang to a Ford dealer they might not be the best choice in 2021.
Anyway, the watch came to me in a bit of disarray... the crystal was broken and the hands were loose inside the case.