Original U.S. Vietnam War 1971 Dated Helicopter Pilot Gentex SPH-4 Helmet with Upgraded SPH-5 Dual Lenses German Ordnance The trench maps never showed

The trench maps never showed the allied trench positions just in case they fell into enemy hands

The lock is marked :

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the angle between the longitudinal axis of the aircraft and that of a fixed star

Original U.S. Vietnam War 1971 Dated Helicopter Pilot Gentex SPH-4 Helmet with Upgraded SPH-5 Dual Lenses German Ordnance The trench maps never showedOriginal Item: Only One Available. This is a United States Helicopter Flight Helmet type SPH 4 made by Gentex. The helmet is in overall good complete condition with the liner, headset, visor, microphone, and upgraded SPH 5 dual tint and clear visor (note the clear visor while it can retract and pull down is missing its control knob). The helmet is maker marked by Gentex and is a size medium and is dated 1971. The reverse of the helmer bears an