… Unused postage, revenue or similar stamps of current or new issue in the country in which they have, or will have, a recognised face value; stamp-impressed paper; … cheque forms; stock, share or bond certificates and similar documents of title. …
Explanatory notes
… 49.07 ‑ Unused postage, revenue or similar stamps of current or new issue in the country in which they have, or will have, a recognised face value; stamp‑impressed paper; … : (a) Vouchers in the form of stamps sometimes issued by retailers to their customers as a rebate on purchases, …