Mauritius "Post Office" stamps
The Mauritius "Post Office" stamps were issued by the British Colony Mauritius in September 1847, in two denominations: an orange-red one penny (1d) and a deep blue two pence (2d). Their name comes from the wording on the stamps reading "Post Office", which was soon changed in the next issue to "Post Paid".
Source: Wikipedia — Mauritius "Post Office" stamps (CC BY-SA 4.0)