I believe the low sidewall of the early design forestock was there, originally, to accommodate the cartridge cut off and did not effect the bolt removal release. While the cartridge cut off was never a feature of the production No4 rifle, the boss for it appears to remain on the front right of the receiver. The cut off was a part of the 1930's design rifles. Image of the 1933 trials rifle from the internet (I don't have one of those, wish I did) as is the image of Proctor with one that was converted to a sniper rifle.
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Lee Enfield .303 No.4 MK1 bolt action trials rifle, 25inch barrel with aperture sight graduated to 1300 yards, the action fitted with magazine cutoff catch, the bolt with early style cocking knob, early style shaped foresight protectors, the receiver with milled pocket for the safety catch, the wrist joint stamped with a crown and GR Enfield 1933 No.4 MkI, the receiver stamped with sold out of service arrows along with 'Fultons Regulated', the butt stock fitted with brass disk, serial number A0846 to wrist joint, bolt and forend, Birmingham proofs. Fitted with a period leather sling. Estimate £800 -1,200
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