I adore wardian cases, terrariums and the like.
Imitation cases are usually zinc and plexiglass ,like this one I spotted at a local market.
You can tell the age of a real one by the thickness and color of the glass.The glass will most often be 1/4 inch to a 1/2 inch. They are always quite heavy. Antique wardian cases are one of those antiques that you can never go wrong investing in. There is always a demand for them so if you find one, go ahead and indulge.