They do exist, and they are still produced, but somehow we hardly see them on letters.
Although this post isn't about a recently issued sheet, (1997), it's more then special.
I didn't know if I had to post it under 'special stamps' or 'special sheets' as both apply here.
|New Zealand - triangular sheet with triangular stamps|
It's a triangular sheet, with 4 triangular stamps in it.
Each stamp is repeated twice, so there are only 2 different stamps.
The sheet was issued for the Wold Philatelic Exhibition 'Pacific '97'. It celebrates the centenary of the first pigeon-gram. At the bottom of the sheet, the flight of a pigeon is drawn.