That is an ADORABLE Mr. John, love the shape, the lining. My thought would be 60s, maybe 70s, but more likely 60s.
it is nothing like a bowler, though, Zannew, you might want to peruse our section about hats here at the VFG, especially if you handle them on a regular basis. also, i have a couple of books that i find very helpful, one by our member here, Susan Langley, and i LOVE my hat book by R. Turner Wilcox, however that was written in 1946 so doesn't have more modern vintage in it.
we used to call those cruiser hats, or a (ladies) version of a pork pie. very cute!