Is the fabric a knitted or woven one? It looks from here like a wool knit bonded to a synthetic backing. But, really, in a photo it's hard to tell. If that's what it is, I would place it later into the 50s. I have a very large number of 50s & early 60s dresses and suits in what looks to be the same or similar fabric, and the 50s ones are latter 50s. I have not personally seen a wool knit like what I think yours is much earlier than that....
And, btw, it's a lovely dress!