That’s because the brand is very special: a red Mauritius. This is one of the most famous and rarest postage stamps in the world. There is also Blue Mauritius. These stamps were printed more than 170 years ago.
Among other things, the Red Mauritius landed on envelopes that were used to send invitations for a costume ball on the island of Mauritius.
There should be only three copies of these envelopes. Queen Elizabeth II of England owns one of them.