Lately, rusted dies are being noticed by collectors. It is assumed that dies exhibiting rust were in storage for some time prior to or between use. Most of the rusted dies identified are on the reverse. It is easy to imagine that a stockpile of reverse dies could occur, given that they were consistent from year to year. The obverse dies took extra preparation by adding the date, and could not be stored for use in another year once the date was punched. Mint photos reveal that dies were annealed, hubbed, and punched in large batches.
The ambitious collector will want an example of each known rusted die, forming the Rusted Dies Match Set. They really are splendid.