Duplicate means to reproduce, Mass production , remake, refashion ,rebuild, also means to copy, reproducing replicas Which might need to be adjusted i.e Square, trim, cut off corners and smooth .
So as you can see a carefully chosen word for selling off slightly off speck parts to unsuspecting customers especially a long way from home. Still going on today ,
i was an inspector of aircraft parts sent to the Antipodes and many where rejected as out of manufacturing specs!!!!!!!!!!
Regards
Clive