Before leaving the triangular stamps for what they are, I can't skipp the european issues.
Small countries as Monaco, Liechtenstein, San Marino and the Vatican City, are known to issue lots of stamps for commercial reasons. However, the quality is outstanding.
As it comes to triangular stamps, I have chosen one issue of Monaco, and two of San Marino
Other countries with triangular stamps :
The Netherlands with an issue of 1936 (mind the cancellation : ADRESSEER VOLLEDIG : meaning: write down the complete address)
The Hungarian contribution to triangular stamps :
And yes, there are many many more triangular stamps, but it's time now for a new page in the world of 'odd stamps' ....