I agree with early 60s. The collar treatment is cool!
Just a note: chiffon can be made of silk, polyester, nylon, or blended fibers, so when listing this, it helps if you can state both the fiber and the fabric type, i.e., "nylon chiffon." Which is probably what this is if it's lined in nylon. But if you don't know, that's fine! It's just that people get into thinking that things like chiffon, gabardine, etc., describe the fiber content, but buyers (like me!) will often want to know, or at least have a good guess, as to what the fiber is. I'm always having to e-mail sellers to ask this question, and the responses I get indicate that they thought these terms would tell me what the fiber was. I do tend to be rather picky about such things, but knowing the fiber tells me whether the item is likely to be low or high maintenance--which is important when I'm buying apparel for myself.