Name: 1888 telegraph stamps
Issued by: Kingdom of Belgium
Type: Definitive
Year: 1888
Sides: 6
Currency: Belgian Franc (BEF)
Telegraph stamps are similar to postage stamps, but rather than being applied to letters and used in the post, they are applied to telegram forms as proof of payment.
The last telegraph stamps, issued by Honduras.
Image from Government of Honduras on WikipediaThe four telegraph stamps
Images from Government of Belguim on WikipediaThe stamps feature the head of the second king of Belgium, Leopold II.
GetArchive / Hexagonal Stamps / https://garystockbridge617.getarchive.net/amp/topics/hexagonal+stamps
Stanley Gibbons / Telegraphs / https://www.stanleygibbons.com/shop/commonwealth/telegraphs
Wikipedia / Telegraph stamps / https://en.m.wikipedia.org/wiki/Telegraph_stamp