… Unused postage, revenue or similar stamps of current or new issue in the country in which they have, or will have, a …
Explanatory notes
… for receipts or certificates). “Postage due” stamps for surcharging understamped letters, etc., are also included. … paid” postal marking. (C) Other stamp‑impressed paper such as official forms, blank forms (e.g., for legal documents subject to revenue stamp duties), printed or embossed with …