This gorgeous Maxi Dress was produced in the 1960s/1970s. It just screams "Abigail's Party".
The Dress is made from a mid-weight purple synthetic fabric - probably polyester.
It has echos of 1940s design with a deep V Neck, dropped shoulder seams and long slim sleeves that gather at the shoulder seams. 
The Dress gathers gently under the bust and then flares out into a long, slightly A-line skirt.
The open back of the Dress has straps across it creating a cut-out ladder effect.
It fastens up the back skirt with a simple zipper.
The Dress doesn't have a manufacturer's label and the original size tag has worn away. The washing instructions say that it was "Made in England".
The measurements are as follows when the Dress is laid flat and measured from the back -Underarm to underarm 16.5", sleeves - shoulder to cuff 22.5", across the waistline 15" and length - shoulder to hem - 54". It weighs 400g.
This equates approximately to a Size 32" bust or a modern UK Size 6-8 but please do check your own measurements before purchasing (allowing some space within the garment so you can move!).The Dress is generally in good pre-loved condition with no significant damage.

Should you have any questions about this listing, please don't hesitate to get in touch and I'll do my best to help.