retree
noun
re·tree
rə̇‧ˈtrē
variants or retree paper
plural -s
: paper that is imperfect or slightly damaged (as by dirty stains, specks, or pinholes occurring in the process of manufacture)
packages of retree are often marked R in the U.S. and XX in Great Britain
compare cassie paper 
Word History
Etymology
retree probably from French retrait withdrawal, retreat, from Middle French