This is a security device that goes on the back of a Star Trek "monster maroon" costume.
Print this with the flat side down. The perfectly flat side is the bottom. I still can't figure out how to get Fusion 360 to export these things so they're not rotated weird. Drop me a comment if you know.
I didn't try this with a metallic filament, but that might be interesting. If you paint it, it doesn't matter what color filament.
I didn't sand this at all. The detail on it pretty much masks any filament issues so just slap a couple of decent coats of paint on here and you're good. I used a Rust-Oleum brushed nickel color that had some good metallic hints to it but wasn't reflective.
Glue a pin to the back
I bought "butterfly clutch blank pins" - these are the same things you see on lots of pins, where you pinch the pin back to release it. You can get these "headless" where it's just a pin and the back. Super glue one pin to the back of this and you're set.
There are a lot of photos of the screen-used security devices (it turns out one was a kitbashed tank wheel, which explains a lot of the look). I based mine on that and a commercial one that's available. It's about halfway between the two. I kind of guessed on the size based on the size of the fabric strip it attaches to.