The Webley Osprey was the rifle that replaced the Mk III as the top-of-the-line, fixed-barrel model. It was a sidelever tap-loader with an extraordinarily heavy barrel, about 3/4” in diameter.
The Hawk barrel-cocking rifles were introduced about the same time as the Osprey; it quickly went through 3 generations of sub-variants.
Though stocks, sights, piston seal materials, and other details continued to evolve, many parts from these guns ended up in later models that lasted well into the 90’s—the Osprey begat the Tracker and Viscount, and the Hawk the Vulcan, Victor, C1, and others.
As this old analog fellow is wont to do, I have to recommend books, LOL: Chris Thrale’s “Webley Air Rifles” is an excellent and well-illustrated history. John Walter’s “The Airgun Book,” editions 1 through 3, is also a super history of this era of European airgunning.