There was a time, when sheets were square or rectangle, with new printing techniques, it's easier to cut sheets in any shape.
With stamps and sheets however, it's still an excpetion to see a sheet cut in a special way.
Mainly because it's harder to take out stamps out of a sheet that is not square or rectangle, but also because of the special cut, less stamps can be put on the sheet.
Less stamps on a sheet, means less income for postal services I guess.
Another difficulty appears for traditional 'country' collectors who keeps their collections in standard albums (with pre-printed pages and the typical plastic window holders to keep stamps from dust and humidity).
Of course they are not keen on round, octagonal, or multi-shaped stamps.
Us, collectors however don't mind, because it brings some fun into a collection.
First i'll show you 'round' souvenir sheets.
Issued by United Nations, 3 round shaped souvenir sheets were issued in 2002 to put HIV and Aids awareness into people's attention. The skyline in New York can be seen, on one of the buildings, the lights show a red ribbon.
One sheet is issued by UN in New York, one in Vienna and one in Geneva.
Here you can admire the Swiss and the Austrian sheet :
The french post issued a sheet that is 'odd' but still will fit in any collectors' album.
The top of the sheet, which represents the Olympic games in Beijing, is cut in a special way, the bottom of the sheet is just straight. The total sheet looks like a chinse traditional house, with several smaller roofs on top of eachother. Issued in 2008.
Finally, we go to Malaysia.
Again, the bottom of the 'sheet' is straight, hurray it fits in the album, but the complete sheetlet is cut like a number 'one'.
The sheet is way smaller then the french one, and has only one single stamp in it.
At the bottom of the sheetlet, the skyline of Kuala Lumpur is depicted.
This sheetlet was issued in 2009.