That's a really nice set! The Tempest and Hurricane are increasing in value these days, too, and you don't see nice early boxed ones much any more.
Just IMHO, these guns are vastly underrated...yeah they are not all cool machined steel like the classic Webley pistols of yore, but they are good-looking, good-shooting, ridiculously durable little airguns, with more power than the oldsters. And the Hurricane, if not as cute as the more compact Tempest, has better sights (click-adjusting rear, taller front, and greater sight radius) which are very worthwhile.
This photo is from the superb book, "Webley Air Pistols," by Gordon Bruce, and shows how the box works. Note your box is identical to this one, but has a removable insert behind the pistol to accommodate a future scope, instead of the insert where the scope rail fits, as seen in this picture (apparently one Insert was included, and the other omitted, depending on which sight option was purchased originally).
I've never seen the target holder mentioned in the caption, but would assume the shallow recess surrounding the target and sight storage is for that.