Tension is given over a pattern stitch I’ve not been able to find in any stitch dictionary; it appears to have been invented just for this garment.

The garment is sized generously:
Small chest measure = 86-91 cm (34-36 in); finished chest = 107 cm (42 in); total length = 65 cm (25.5 in); sleeve length = 46 cm (18 in)..
Medium chest measure = 97-102 cm (38-40 in); finished chest = 117 cm (46 in); total length = 71 cm (28 in); sleeve length = 52 cm (20.5 in).
Large chest measure = 107-112 cm (42-44 in); finished chest = 127 cm (50 in); total length = 71 cm (28 in); sleeve length = 52 cm (20.5 in).