signal mirror: USMC Heliograph #479
signal mirror: USMC Heliograph #479, closeup
signal mirror: USMC Heliograph 479 - Simplex Setup
signal mirror: Friez USMC Field Heliograph Shutter #236 - Five view collage
signal mirror: Features of Model 1905 US Signal Service Heliograph
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signal mirror: US Marines with Heliograph 1915