British patent GB486475 (Publiation Date: 1938-06-03) for elastic fabric. SYMINGTON & CO., Ltd., R. & W. H., and BILLING, G. W. March 30, 1937, No. 9090. The invention relates to garments, particularly but not exclusively intended for bathers or swimmers, made of puckered material rendered elastic by stitching strands of rubber (Fig. 1), following the warp and weft in a zigzag manner. The material is folded and seamed (Fig. 6). The material so folded is provided with a continuous spirally run length of rubber strand e, (Fig. 2), intersecting the other strand a. The garment has a top hem f, Fig. 7, as a runner for draw-strings g.
I have since come across some images of an extant suit: