Hmmmmm. I think that this may indeed be from the 1950s, probably the early part of the decade. From what I can tell in the photos, this is a hat made for the tourist trade or a summer beach hat like those sold at a seaside resort, cruise ship, beach shop, swim apparel shop, etc. The straw is a low grade straw such as raffia or palm and is a bit crudely made (I am not putting it down, however as it is pretty) and it has no finishing underneath. For example it has no head size ribbon (AKA sweatband). I do like the wooly (?) braid sewn atop the straw. I have seen that technique used but usually more for decorative effects. I have not seen an all-over effect as yours is. As for any 2 tone straw mix, that goes back to at least the Victorian era.
It is a very cute hat. You might want to replace that ribbon with a wider ribbon and see if that freshens it up a bit.