The 'Astrolabe'

Location: Bodenham Arboretum, Wolverley, Worcestershire. I call this thing (in my mind) an Astrolabe, but actually it isn't. I think it's a kind of sundial as inside the metallic rings are Roman Numerals which, going from one to twelve, are obviously months of the year.

I'm local to this venue and visit it often but I must find out what it's actually called sometime.