Gregory's Express, Office, San Francisco, full clear blue three-line handstamp (GRE-110) on incoming 1852 folded letter from Nicaragua, matching "Not Paid" in oval handstamp with manuscript "50" clipper ship rate, dropped of by purser for local delivery in Gregory's office, Extremely Fine, a rare clipper ship rate usage, this is one of three examples of this handstamp recorded; with 2011 P.F. certificate. Estimate  $750 - 1,000. $0 (Image)