The presence of wing nuts indicates the bicycle is most likely early 1970s. As Oldyellr points out, the the bicycle is typical of even earlier periods, but most likely it's from the early 1970s boom period, as that's when the vast majority of 10 speeds were purchased. The CPSC (sp?) targeted wing nuts as a hazard in their proposed legislation in the early 1970s. Most manufacturers voluntarily removed the devices in advance of the legislation, according to their own implementation schedule, so there is no specific date when we can say that they disappeared. However, most manufacturers had gotten rid of them by 1975, so the presence of wings usually indicates early 1970s models.

From what I can see, the model appears to be the US-10, which was an entry level model. I had a 1977 St. Etienne with Reynolds 531 butted tubing, which I sold off last year. I do have some info on St. Etienne, but first I'll give the Luker the chance to re-post with his info.