It could be just the effects of taking a photo of a printed item, but the colours look very bright and unnatural. Almost as if this was originally a black-and-white photo which had been colourised. OC Richard, since you can inspect the original, do you think this is the case? That might help narrow down the time frame. Colour photography was readily available by the 1950s and 1960s, but many photos were still taken in black-and-white because it was cheaper.

Other than that, based on the hair styles and such, around 1960 (plus or minus a few years) would be my guess as well. Could even hark back to the late 1940s, though. (?)