Infor on Wassily Chairs with Made in Columbia, S.A sticker  

I'd like some information on a pair of Wassily Chairs given to me. I have a pair of the Dark brown leather and chrome Wassily chairs, that were given to me. I have searched all over for stamps, embossing, stickers of any kind showing the manufacturer,i.e knoll and have not found any with the exception of a white round sticker on one of them stating made in Columbia, S.A. the chairs seem to be correct with all chrome (no plastic ) caps and black screws the brown leather is a dark brown and the seat has a light cream almost white canvas backing sewn to the bottom.
My question is, who might be the manufacturer of these? My friends who gave these to me said they had them since about 1968, so any ideas on the manufacturer? Did knoll ever have any manufactured in Columbia,if not,who did? Any help with information is greatly appreciated.