The lens is pre-WWII made 1938/9, it looks like the Cook & Perkins Helical may be later. There are references to military lenses being remounted in Cook & Perkins focus mounts/helicals for civilian use after the war. It will be difficult to ascertain the original use of the lens.
It does look like the helical may accept the Contax mount Sonnar as well, they aren't normally threaded internally. The company were based in Pembroke Works, London, N10, they made lens barrels etc for Dallmeyer, and Taylor, Taylor, & Hobson (Cooke) as well.
Ian