Postal seals are a necessity in dealing with letters and packages. What was sealed has a nasty habit of becoming unsealed. Paper gets caught in machines. Putting a package in a bag may cause damage to other contents. In short, paper is sometimes fragile.
The gummed seal or its self-stick relation takes care of these problems. Of course, there are times when postal authorities must open a letter or package to check contents. The postal seal is at hand to reseal. (Figure 1).
The postal seal isn’t the only one in the business - Customs & Excise has a legitimate need to open some parcels to look for contraband or check for smuggling. Their seals a different but yet serve the same purpose. (Figure 2).
Collectors will also find postal, censorship seals used to reseal covers after the censor’s scrutiny. These are covered in a separate discussions of World War I and II censored mail. Figure 3 shows an irish censor resealing label of World War II.