Pins and plating
The pin was invented and patented in 1917 in France by a Monsieur Prost, who tried to persuade the British authorities that it might benefit the Mills grenade. While it was adopted by the French for their grenades, 500 of the pins were distributed to the UK Bombing Schools for trial, after which it was rejected.
In a parallel development, Francis Gibbons (of the Gibbons spring mechanism training grenade fame) patented a very similar pin, patent GB111949A. Likewise it did not see use in service.
During 1916 and 1917, the British Government supplied the Belgian Army with Mills grenades as and when asked. However, in December 1917 this was formalised in a monthly demand for 20,000 No.23 MkII, and from mid-1918 No.23 MkIII. With the changeover from 23II to 23III, the Belgians asked for the grenades to be supplied with the new French safety pin.
In addition there had been at least one Belgian requirement for 8,000 dummy grenades for training from Britain in July 1917, and there may have been additional during 1918. The Gibbons company had supplied reject grenades, electro-zinced, as training dummies to the British Army from December 1916, and so it is reasonable that the Belgian Army were similarly supplied.
Therefore surviving examples of Mills with Prost type pins (assuming the pins are original to the grenades) could be from the small number trialled by the British Army; training dummies (some electro-plated) kitted out with Prost pins used by the Belgian Army (which would have replaced any ordinary pins with Prost after mid-1918); or from Belgian Army service grenades (definitely non-plated).
Without getting heavily involved in a discussion of electro-plating, dipping a steel or cast iron object in molten zinc for rust proofing (galvanizing) gives a matt grey surface, while true zinc electro-plating gives a shiny metallic finish, which can wear off with use. Both of these finishes are seen in surviving Mills examples. It is also possible that nickel may have been substituted for zinc in the electroplating process, depending on what chemicals the manufacturer easily had to hand.
Tom.
