This dress is a mystery to me. I think it's brand new. I thought it was vintage when I bought it. I thought maybe it might be home made, which would account for its lack of label, but it does have a lot tag and that belt seems professionally made. I looked up what's written on the tag and found a simplicity pattern from the 60s that seems similar to this dress. Maybe it's a professionally made simplicity pattern? Thanks for your help!
It's professionally made, probably by a job lot manufacturer who is contracted to make lines for retailers, like department stores. Their dresses are often not labelled, because they are labelled by the retailer, not the manufacturer. Sometimes they are not labelled at all. It looks early 60s to me, c. 62-64ish. A modern manufacturer wouldn't dare use that font for the pure silk label!