This is a long/maxi, 1970s dress by Kati at Laura Phillips.  It is a size 8 although the label says a 12.
It measures 140 cm in length down the centre back, 40 cm across the chest from under each arm hole, and the sleeves are approximately 25 cm in length.  There is a peplam detail at the waist, 6 buttons, decoarted with ric rac top and bottom.  There is a white frill round the  neck and the sleeves are also white.  There is no longer any elastic in the sleeves.