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cod1

Cash-on-delivery envelope. Switzerland. 1875.  The envelope could be used within Switzerland and Germany.  An envelope was used so that an invoice or letter could be enclosed.
pneuenv1

Pneumatic post envelope. Germany. 1889.  For use within the Berlin pneumatic post.
mexico_airenv

Airmail envelope. Mexico.
chileenv15c

Envelope. Chile. 1873. 10 centavos.