I bought this back when baby me was in hs. I remember getting it and being excited about it and then never wearing it lol. I do remember trying it on. Been in a closet for nearly 10 years. There are no issues that I can see. I'm 99% sure this is the medium size because I was a tiny in hs and i didnt measure myself prior to 2018. I looked for a size tag all over but there is none. I can do a flat measurement upon request. 

Bust

M 96 cm // L 100 cm // 2L 104 cm

Length

M 56 cm // L 57.5 cm // 2L 59 cm (coat), M 50 cm // L 51 cm // 2L 52 cm (skirt)

Waist

M 64-100 cm // L 68-104 cm // 2L 72-108 cm

Sleeve Length

M 78 cm // L 80 cm // 2L 82 cm (from center back)