1945 PRO MONTEPIO
(For the benefit fund collected by a society for its members)
GALVEZ page 392 lists these and states that they exist overprinted
Sawtooth (serrated) rouletted.
"Sin Valor Postal" =without postal value
Some cinderella stamps from the French Island of Ile Roy were based on these Spanish labels.
"Ile Roy" is not an Island but a restaurant run by Pierre Vion (France) c1974
Discussed in Gibbons Stamp Monthly May 2006
My homemade Page,
you are going to need 4 pages, if you collect the overprints as well.