In 1917, the British Army introduced a new hand grenade as the "No. 34". The No. 34 following the new German Army "Model 1917 Eierhandgranate" hand grenade which was introduced earlier that year. The Eihandgranate proved a small, very portable hand grenade with a pull wire feature, making it more useful than the common Model 24 "Stielhandgranate" ("stick grenade") of 1915. The British followed suit with their design of the No. 34, adopting a similar tear-dropped shape body with a smooth external finish and pull wire feature. Additionally, it was of a compact size which allowed several to be carried forward by one man while its lightweight increased throwing distances.
At its core, the No.34 utilized an internal percussion delay fuse mechanism. The weapon relied on the user removing a pin to which the grenade was then smashed down against a hard surface to actuate an internal plunger arrangement. The plunger then fell onto a wire, severing it, and fired off the primer cap. The primer began the delay fuse which was designed to burn into the detonator. From there, the operator needed to throw the grenade at the desired target area or suffer injury.
The No. 34 appeared across four major versions as the Mk I, Mk II, Mk III and Mk IV.