Mk4G Protective Flying Helmet

[on transport box's interior]
Modification Record
Helmet Protective Flying Mk.4.G.
Size Medium Long
Helmet Serial No. 19396
MR1 029-Iss.112
HM 024
Not for NVG use
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[on transport box's exterior - 1]
Ref: N022C/7702165
Helmet Aircrew
MX 4D.
Size Medium
Serial No 18390
Ref: N022/1302469
Carrying Bag.
Quantity 1.
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[on transport box's exterior - 2]
Primary Standard Package
Packed by Helmets Ltd
Date 26 Oct 1988
OTT A66al 3915/88
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[delivery address]
GEC Ferranti Defence Systems Ltd.,
Display Systems Division,
South Gyle Crescent,
Edinburgh EH12 9HQ,
Scotland

The Mk.4A Flying Helmet is current Royal Air Force / Royal Navy / Army Air corps issue and superseded the Mk.3C helmet in the 1980`s. The shell is made of glass fibre impregnated with polyester resin and lined with shock absorbing expanded polystyrene; the interior is fitted with a multi-point adjustable webbing harness system with adjustable independently suspended earcups. The helmet has a locking clear inner blast visor and a friction mounted outer tinted visor with a detachable cloth visor cover, avionics consist of twin 300Ω speakers giving an impedance of 150Ω (@ 1kHz) terminating with a 18" downlead and single pin NATO jackplug, mounting blocks allow the fitting of hooks for the P or Q type oxygen mask. The Mk.4A has locating holes allowing the fitting of RAF or similar Boom Mikes. The manufacturer is probably Helmet Integrated Systems Ltd.
The given dimensions are for the helmet alone. Its cloth carrying bag has a girth of 900mm and weighs 145g. The helmet and bag inside its 360 x 310 x 360 mm cardboard transport box weigh 3340g.
Interestingly the packing date is 1988 which is two years before GEC took over Ferranti Defence Systems so it would suggest that as a standard Helmet, the item was packed and held in store before shipment.