Vintage World War II US Army Forces Navigational Aids

Offered are two World War II navigational aids. The black plastic disk is a Time Distance Computer Type D-4 U.S. Army Air Forces, circa 1943. The disc measures approximately 4 3/8" in diameter with a metal center core. Made in USA by J.B. Carroll Co.

Front Scale: True Altitude, Air Temp, Press. Alt. (ETA, Air Speed )
Back Scale: Cal. Air Speed, Air Temp, True A.S. (pressure Altitude, Density Altitude)

The white disk is made of a heavy card stock with a metal center core. It is a time-distance computer. The disk measures approximately 3 1/2" in diameter. No maker's information.

Front Scale: Miles, Hours, Minutes
Back Scale: Altitude, Air Speed, Temperature Centrigrade

Nice military collectibles in very good vintage condition.