Chelsea Filter Magnifier Style_Accessory and through the viewfinder you

and through the viewfinder you see a scale

not only opens small screw-backs (18mm) but also large watches

The battery icon on the display means low battery

For measuring specific gravity

For the non-expert: if you can see inclusions (e

Chelsea Filter Magnifier Style_Accessory and through the viewfinder youSummary The original Chelsea Filter, as developed at the Chelsea College of Science and Technology in 1934. Do not confuse this with the many copies. Detail Many stones appear to change colour when viewed through the filter. Originally designed for detecting synthetic emeralds, nowadays the Chelsea filter is an invaluable aid to identifying many other gemstones. It can give an indication that you have an emeralds and aquamarines, though not a