Portuguese philately - type of paper used for stamps

Between 1912 and 1931 Portugal issued a series of stamps called CERES for
use in Portugal and the Colonies. This series was printed and reprinted by
a number of different printers and consequently ended up being printed on
quite a number of different types of paper -- one printer even went so far
as to print a large number of these stamps on postcard stock. One of the
most used papers was called papel pontinhado. So far I have been using
pontinhado (in italics) because I have not been able to find equivalent in
English for this type of paper.

Quite some time ago I asked on this group for help and received no replies
so I shall try again. So far, through the Simoes, Afinsa, and De Santos
catalogues I have been able to ascertain that pontinhado paper IS NOT
standard, chalk-surfaced, granite, laid, woven, glossy, lozenged or native,
and that it has not been used since the late 40s. So I return to the
experts: what the heck is this papel pontinhado? I have some of these
stamps in my collections and even under an electronic microscope I cannot
differentiate these stamps from the same stamps listed separately under
papel liso.

Referrals to philatelic newsgroups have been followed but without success.
Requests for information to the Filatélia Division of the Grupo CTT
(Portuguese Postal Service) have not been answered.

Thanks in advance for all help.
--
Tony Vella
Ottawa, Ontario, Canada
http://www.amedialuz.ca/