The Panamka brimmed hat (also called a “Panamanka”, “Panama”, or “Panama Afghanka” hat) was issued to Soviet soldiers serving in tropical climates and widely exported to Soviet-aligned guerilla movements worldwide.
Sample 1:
Outside strap is plastic. 
Back side has 2 rows of vent holes.
This example was recovered in Rhodesia (now Zimbabwe).
Sides:
Buttons are completely smooth with no star, hammer and sickle, or any other identifying insignia. The blank buttons are a characteristic of Soviet export uniforms (source: https://www.usmilitariaforum.com/forums/index.php?/topic/300449-soviet-afghanka-from-grenada-1983/&tab=comments#comment-2413988).
Top:
High “beach ball” 4-panel construction similar to French bush hat. Note that the design pre-dates the French bush hat, introduced in 1949, since the Panamka hat’s official name, M-38 Field Hat, which indicates it was accepted for service in 1938. A supposed WW2 era example made out of different fabric can be seen here: https://oorlogsspullen.nl/product/original-wwii-russian-m38-tropical-panamanka-hat/.
Inside:
Blue-green inside with faux leather plastic sweatband. Unknown if it once had a stamp or if it was manufactured sterile like the Soviet Tropical Export Uniform which uses the same fabric.
Usage Photos:
Soviet-Afghan War:
A scene from the Red Army’s withdrawal from Afghanistan through the Uzbek town of Termez (from https://www.rferl.org/a/Twenty_Years_After_Pullout_SovietAfghan_Conflict_Still_Haunts/1493064.html). 
October 15, 1986: Soviet soldiers are returning home from Afghanistan. Alexander Grashchenkov / RIA Novosti (translated from original Russian; from https://www.iwp.edu/articles/2020/12/18/mass-murder-in-afghanistan-40-years-of-conflict/). 
October 18: 1986: Return of Soviet soldiers-internationalists from the Democratic Republic of Afghanistan. Yuri Somov / RIA Novosti (translated from original Russian, from https://commons.wikimedia.org/wiki/File:RIAN_archive_644465_First_stage_in_the_Soviet_troop_withdrawal_from_Afghanistan.jpg).
These hats were commonly photographed being worn by Soviet soldiers in the Soviet Afghan War (1980’s).
Insurgents:
Movimento Popular de Libertação de Angola (MPLA):
Zimbabwe Africation National Liberation Army (ZANLA):
ZANLA was the military wing of the Zimbabwe National Union (ZANU), one of the two major guerilla groups who fought against Rhodesia. Their leader was Robert Mugabe.
https://www.alamy.com/stock-photo-zimbabwe-zanu-patriotic-front-troops-loyal-to-robert-mugabe-come-in-33023463.html (cannot show photo directly due to licensing issues)
Frente Nacional de Libertação de Angola (FNLA):
Opponents of Soviet-backed insurgents sometimes used captured Panamka hats.
https://www.gettyimages.com/detail/news-photo/mercenary-portuguese-fnla-in-angola-in-1975-fnla-national-news-photo/120398940 (cannot show photo directly due to licensing issues)