The typesetters made many errors. In addition, they apparently ran-out of some letters and resorted to replacements such as an inverted V for A. Stamp collectors soon recognized these varieties, and collecting them remains popular today.
In June 1904, Canal Zone governor Major General George W. Davis recognized the need for stamps. Rather than wait for the US to ship them, he arranged for small purchases of the newly overprinted Panamanian stamps. On June 23, 1904, Davis asked Panama's secretary of state, Tomas Arias, for an initial order of 1,000 Colombian pesos in stamps as follows:
500P in 10-cent, 400P in 5-cent, and 100P in 2-cent stamps. At the time, Panama did not have its own currency, and US and Colombian money circulated freely at the rate of one US gold dollar to two Colombian silver pesos. The actual cost to the US, however, was $240 in gold because the arrangement was for payment to be made at a rate of 20 percent of the face value in Colombian silver pesos.
By most accounts, a Panamanian postal system employee used a rubber handstamp with a bluish-violet ink to overprint the stamps, a process that produced many varieties, such as CANAL ZONE inverted, diagonal, and doubled. In addition, some stamps did not get a Canal Zone overprint, and these can only be distinguished when still attached to another with the proper overprint.
On June 24, 1904, the Canal Zone post offices at Ancon, Cristobal, and Culebra placed the new stamps (Scott 1-3) on sale. Used stamps appear on and off cover from these towns. On June 25, officials opened the other six Canal Zone post offices. Covers from any of the original post offices are uncommon, and those postmarked at Gatun are very rare.
Officials placed a smaller order for overprinted Panamanian stamps in July, raising the total number of stamps delivered to the Canal Zone to 2,600 2-cent, 8,500 5-cent; and 5,250 10-cent. However, the expected shipment of overprinted US stamps had arrived by July 15, and Governor Davis informed the Panamanians that no further need for their stamps existed. At close of business July 17, postmasters took the First Series stamps off sale, and on September 14, authorities burned 700 5-cent and 304 10-cent stamps, leaving a final total of 2,600 2-cent, 7,800 5-cent, and 4,946 10-cent stamps issued.
Because very few of the First Series stamps sold in the short period they were available, stamp collectors find them very desirable, especially on cover. This demand has resulted in relatively high values. Because a crude rubber handstamp made the genuine overprints, counterfeits appeared for sale on the Isthmus almost immediately. Counterfeits appeared on covers either passing through Canal Zone post offices or on envelopes with forged postmarks. Many counterfeits in various colors of ink were apparently made for the tourist trade. Some are crude and easy to identify, but very dangerous copies are known both on and off-cover. Collectors are strongly advised to have any First Series stamps they wish to buy or sell expertized at one of the professional philatelic groups in the United States.
Plass, Gilbert N. Canal Zone Stamps. Atlantic City, NJ: Canal Zone Study Group, 1986.