Details and Image
|Date||Scale Length||Area of Use
|Disk & Linear||Felsenthal E-6B||Felsenthal||USA||Aluminum||diam. 12 cm||Navgation for Aviation
Notes: "There is actually a Wikipedia entry describing the use and history of the E6B device. Apparently it is sometimes nicknamed the ""whiz wheel"" or ""prayer wheel"" and is reportedly one of the few analog calculating devices in widespread use in the 21st century."