Every London Antwerp Diamonds diamond can be sealed in a plastic holder together with a microfilm of the certificate. Not only does the sealing keep the diamond safe from damage, grease and dirt, it is also a guarantee that a given certificate and the accompanying stone actually belong together.

The two layers of the sealing, i.e. the upper window and the bottom card, are held together with a special pressure-sensitive transparent adhesive to assure that the elements are irreversibly bonded. When opening the sealing, the printed pattern on the bottom card will be disrupted

The material used for the window is clear, colourless, scratch resistant polyester. The combination of flexible but strong material and the layered design ensures that the sealing provides protection against normal wear and tear. The same resilient material is used for the holder on which the diamond itself rests. This diamond holder is constructed in such a way, that the culet is safely held without touching the bottom card, thereby providing maximum protection against damage. The advantage of this transparent and colourless diamond holder is that the diamond seems to float in the window, so that brilliance and fire are not diminished.

The sealing can be opened without any instruments or even scissors: it suffices to peel off the back layer. Once it has been opened, however, it cannot be resealed. Even if one tried to glue the parts together again, the fractured red bars and the cryptoprint text cannot be undone.