signal mirror:
Keuffel & Esser USFS Heliograph
signal mirror:
Keuffel & Esser USFS Heliograph
signal mirror:
Keuffel & Esser USFS Heliograph Simplex Setup
signal mirror:
Keuffel & Esser USFS Heliograph Duplex Mirrors
signal mirror:
Keuffel & Esser USFS Heliograph Shutter on Tripod
signal mirror:
Keuffel & Esser USFS Heliograph Cases
signal mirror:
Kueffel & Esser USFS Heliograph Mirror Bar Case
signal mirror:
Keuffel & Esser USFS Heliograph Mirror Bar
signal mirror:
Keuffel & Esser USFS Heliograph Case
signal mirror:
Keuffel & Esser USFS Heliograph Case
signal mirror:
Keuffel & Esser USFS Heliograph Shutter Views
signal mirror:
Keuffel & Esser USFS Heliograph Mirror Box
signal mirror:
Keuffel & Esser USFS Heliograph Mirror Box
signal mirror:
Keuffel & Esser USFS Heliograph Mirror
signal mirror:
1913 Keuffel & Esser Heliograph Diagram.
signal mirror:
US Signal Corps Heliograph Mirror Bar Case K&E 1/2
signal mirror:
US Signal Service Heliograph Mirror Bar Case K&E 2/2