Substraction is possible (via the 9s complement method) using the red numbers shown to the right of each chain. Clearing of the result register is achieved by turning the knob at bottom right until all digits show zero.
The neat wooden box shown above was hand-made by the original owner. It has a little compartment for storing the stylus. The original owner was Chinese and decided that he preferred the abacus (because it was faster!) and left this wonderful piece on a shelf for many years.
Model 16 (top) and Original 'Classic' Model
The Model 16 (top) is quite a bit bigger than the 'classic' Golden Gem Adder, which is shown with its cover off and chains exposed.
Golden Gem Model 16
Other Chain Adders
Pico Chain Adder
Precision Instrument Co. New Jersey (source ebay)
The Pico Chain Adder (shown above) appears a near duplicate to the Golden Gem, but with a gray crinkle finish and exposed brass plate and trim hardware.
The Dainish Dux Chain Adder appears roughly similar in shape and function to the Golden Gem, but is more handsome and much less commonly encountered.