Thanks Jill and Nina,
I also noted the Oklahoma connection when I Googled. But the problem is that it was first produced in 1943, and I read somewhere that it was not even originally called Oklahoma (let alone O.K.), but something else, only changing its name when the critics (what do they know?) slated it. I can't imagine that it reached Leeds, Scarborough, or wherever our Colisseum is, until at least 1950, which we seem to agree is much after the clothing styles in the photo.
Good idea to try the Photographic section (I didn't know about it!).
Cheers
Tim