Paid about 6 times catalog value for this one (i.e. $6) but I had been searching for a couple years for an elusive example of a 1 sen tin-zinc coin in good MS without tin pest.
These coins were made as an emergency stopgap, not as a collector's item and were never intended to last more than a couple years. The tin-zinc alloy used is highly unstable, and if left exposed to cold temperatures, the coin will disintegrate into grey powder.
I owe you all a thread for my Japanese collection, but I have been dragging my feet about getting images, and have also been working on upgrading the pieces that can be upgraded without breaking the bank.