pure finder

noun1

1. •
   (no longer used) Someone who collected dog faeces for sale to tanneries (which used it as a siccative for bookbinding leather). Undertaken by poor people in Britain in the 18th and 19th centuries.

   • The pure-finders meet with a ready market for all the dogs’-dung they are able to collect, at the numerous tanyards in Bermondsey. — 1851