That is a nice find. It is not a dress (although I can see some young woman wearing it as such), but it is lingerie. A nightie or summer nightgown, styled after an antique chemise. It is from the earlier days of VS, back when pretty much all they sold was romantic Victorian styled lingerie, nightgowns and blouses. I actually had one very similar, but mine was shorter. The tag is not the very first years, but is an older early tag. I cannot say for sure what year it is from, perhaps late 1970s to early 1980s. Hopefully another member will come along who know the VS line better or can recall actually seeing this back in the day.
It is very pretty.