vintage billabong gilet ~ S ?

vintage billabong jacket captain kirk rock wash corduroy made in australia circa 1991 100% cotton used size S? (pit-to-pit measures 53cm, back collar to waist 59cm). very good used condition. this was once a sleeved jacket & was cut by previous owner. snap-button closure & all elastic remains stretchy. some wear to back graphic & minor pilling to corduroy in shoulder area. tags read medium however fits small like modern S.