My dad took to wearing a Stetson on occasion in his late 40's, around 25 years ago. In Oslo. I'm not sure exactly which type, but one of the fedoras.

I'm not so sure most people in Oslo would have agreed it was "acceptable" but he didn't care, and it's not like anyone would call him out on it.

I'm in my late 40's now, and kinda want to wear a hat but I think I'll pick something which stands out less.