A side project I made using this PDF pattern. The shell is made from a leather remnant I got at a craft store, while the visor is some "blacksmith" leather I bought years ago and have never found a use for. I would've preferred the visor to match the crown in color, but a number of experiments failed to produce a construction and finishing method that wouldn't bleed dye and deform when wet or "crack" when creased. I wanted this cap to be functionally indestructible. The blacksmith leather is extremely dark brown, but appears blue-black in the photos due to outdoor light (it was slightly overcast this morning). For the same reason, it also has a smooth leather lining inside the band with a replaceable cotton sweatband hot-glued into place.
This is what the cap originally looked like. However, after completing it on Sunday, I decided that the bright gold buttons and lacquered brass buckle were too ostentatious and military-looking.
Luckily, I had some antiqued brass-plated buttons and two of these 1/2-inch buckles from Tandy Leather, and an uncle of mine had given me a bottle of Blacken-It. I sanded the lacquer off the remaining buckle, darkened it, brushed back the Blacken-It finish with steel wool (it's still darker than it appears in the photo), and put together a new chin cord yesterday. The cords are just attached with twisted copper wire through a pair of holes on either side, so they can be easily removed and replaced with needlenose pliers/clippers. The other cord will probably be used for a costume hat project.
While this style is recognized in the West as a Greek fisherman's or sailor's cap, it was common peasant or working-class headwear, especially in Eastern Europe, so it would also work for any early 20th-century costume. And because it's made of leather, it also counts as a motorcycle cap. I like to think the functional chin cord would also work better for that purpose than the simple chain that a lot of them feature.
I modified it in two ways: First, the band is a bit wider than in the pattern, for more headspace, and second, I also made the visor wider from side to side. This forces the ends to be pulled in more when stitched to the band, which causes the visor to curl down more, protecting the eyes better from the sun.