Rarity can be related to a machine which, unusually for that model, is still working. Or a collector’s item may include a scarce program module or some other accessory, component or characteristic which increases it’s rarity value. Chess computers restricted to release in just one country may appear from elsewhere to be very rare. In this and many other cases time will tell how many there really are.
I make no claim of exceptional rarity for most of these chess computers. In the majority of cases I have no idea how many survivors there are. The approach I take to this issue is this. If a chess computer is found only in a limited number of known collections, and appears very infrequently on the internet, including Ebay, it qualifies as rare for the purposes of this feature. Other chess computers, seen a little more often, have been included if they are of particular interest.
Hopefully this feature will include some models, photographs or information you have not seen before. At the very least, for the hard core collectors, a pleasant browse through the rare, reasonably rare and not so rare.