Odd Shapes On Stamps (Including Hexagons)

Hungary
50th Anniversary of Budapest Research Reactor
March 25, 2009
The hexagonal-shaped stamp depicts hexagonal form of the nuclear reactor.

A hexagonal-shaped stamp - BEAUTIFUL -- but I would expect it must be a perforation machine nightmare! I can't imagine how they did it back in the late 1800s on the Telegraph stamps. It's as interesting a detail as the stamps. It would be great if someone has information on how they perforated the hexagon issues in the 1800s.

Also, some of the geometric stamp issues on this thread are great! Thanks to everyone who has taken time to contribute,

Argentina
Centenary of UPAEP
March 19, 2011
The stamp celebrates 100 years of UPAEP (The Postal Union of the Americas, Spain and Portugal).

Austria
New Ways - Carrier Pigeon
February 13, 2019
The low-resolution carrier pigeon recalls the earliest days of digital technology.

Denmark
Danish Diabetes Association
August 30, 1990
The stamp depicts microscope image of insulin crystals.

Germany
Microworlds
June 8, 2019
The stamp depicts the electron microscope image of palladium in the form of dendritic crystals.

Netherlands
Week of the Postcard
April 18, 2011
The design features stylized flowers.

Germany
Change of Perspective
October 10, 2019
The motif by VectoriX shows the optical illusion of an impossible 3D object.

Sweden
Snow Crystals
November 18, 2010
The stamp depicts hexagonal snow crystals with dendritic morphology.

Monaco
EUROPA - Integration
May 5, 2006
Set of two, one stamp features The Cube by artist Jean-Paul Veret-Lemarinier.

Germany
Optical Illusions
April 2, 2020
Two shades of gray?

Estonia
Centenary of the National Archives
March 3, 2020
The number 100 is part of a maze which is the main design element of the facade of the building.

Liechtenstein
Winter Olympics Sarajevo
December 5, 1983
The design shows a stylized snowflake.

Liechtenstein
European Economic Area
March 2, 2020
The design, entitled Network, uses stylized weave pattern to convey integration.

Andorra
EUROPA - Integration
May 9, 2006
The seamless squares mosaic tiles symbolize European countries.