Special Cancellation Die Hubs
Postmasters and plant managers who
have any of the special cancellation die hubs listed below may use them
for the periods designated. At the end of the period, these die hubs must
be withdrawn and stored. Postmasters and plant managers who do not have
these special die hubs may not request them from the sponsors.
— Mailing Standards, Pricing
and Classification, 10-27-05