These magnifiers all have a clear base to allow light to fall on the subject. Double Glass Lens. Used by many photographers. An unusual items.
Clear base allow ambient light to illuminated the subject.
Comes with a lens cover. We use one to focus our view camera. Huge two and half inch lens is permanently mounted over a three inch compartment. It was originally developed to study insects as they have lots of room to run around, but us also great for anyone needing hands-free fixed magnification and a large viewing area. Very popular with stamp and coin collectors.