Quote:
Printed matter also placed an extra burden on the post office, and, from the covers that survive we have learned that old postmarking devices were sometimes retrieved and used to cancel circulars and wrappers.
The Philadelphia 32-millimeter circular datestamp, which was used on first-class mail up through 1866, was evidently brought back into use in early 1868. Another example from the same time period--a genuine 1c E Grill--is recorded in the Philatelic Foundation records (PFC 133477 "Genuine").
A snippet from Scott Trepel's write-up of the stamp for the October 1998 Zoellner sale. Siegel sale 804 lot 226.
edit: added more of Scott's quote