Lot
779 
Panama, 1902, Registration, 20c on 10c Brown Red, blue "6168" handstamp, used with Panama 20c violet (19) pair, tied by "Panama, 1 Sep 1902" duplex on cover to San Francisco Cal., New York (4.22) and San Francisco (4.27) backstamps, Very Fine. Scott No. Panama F5 + 19 (2) Estimate $300 - 400.
On April 14th 1902, postal rates were double. The stock of the provisional registration stamps was surcharged with a "20" over each 10c.