That's quite a classic style, bit hard to date... are there any care/composition labels at all? They might help...
I'm wondering, from looking at the labels in the label resource if it might be 1960s? It seems Top of the Sixes was an iconic New York restaurant... there was a scene in Wolf of Wall Street set there - it was located in the penthouse of a midtown Fifth Avenue Manhattan skyscraper – number 666. Apparently it opened in 1958 so, if McGregors decided to name a line of clothing after it, that would probably sit quite well with the 60s.
It's not a brand I'm familiar, hopefully some of the US members may be more knowledgeable on it...