Dear N___:

You wrote:

>>Are these sentences correct:

>>1-We were dancing as in the Fifties. (restrictive: in the same way they danced in the Fifties)
>>2-We were dancing, as in the Fifties.(non-restrictive: They danced in the Fifties and now we were dancing)

>>Can 2 be used to mean that we were dancing in the same way they danced in the Fifties?
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In most speech, the meaning #1 you give would be understood by most people here, with or without the comma. Technically, your parenthetical interpretations are correct, but we do not speak with commas, so most people would understand either sentence to be what the first says. If you wanted to communicate meaning #2, the best solution is to say it differently such as the way you put it in the parentheses.