In December 1861 the San Francisco, CA USPO began using a fancy cogwheel design to cancel stamps as they entered the mails (for outgoing mail, and in some cases incoming mail if this was entrance into the U.S. mail system).  This was not the only cancellation device in use by the SFPO at this time, however it was the only fancy style and it is unique to this post office. During its lifetime three different types of the cogwheel cancel were used (Types 1, 2 & 3). The main usage period for the cancel was 1862-1867. Oddly enough, after a gap of more than 10 years, evidence of the cancel reappears in 1879-1887. It is not understood why this cancel “re-surfaced” after so many years of not being used.

This exhibit focuses on all three types of the cogwheel fancy cancel, from the early years through its main usage period and finally to the end of its lifespan. Details of each type are discussed along with various postal system usages, both domestic and foreign. Two major routes for mail transportation out of San Francisco were in use during this period; the ocean (Panama) route and the central overland route.

Type 1 cogwheel:

• Has the smallest diameter circles

• 9-9.5 mm outer circle, 5-5.5 mm inner circle

• 16 cogs

• Many cogs have pointy-tips (wedge-shaped)

• Separate from date stamp device

• Observed usage period: Feb 1862 thru Dec 1863

Type 1 cog on 1861 5c Buff Issue
 

Type 2 cogwheel:

• Similar style to Type 1 but with larger diameter circles

• 10-10.5 mm outer circle, 5.5-6 mm inner circle

• 16 cogs (same as Type 1)

• Most cogs are blunt/squared (not wedge-shaped)

• Separate from date stamp device

• Observed usage period: Jan 1862 thru Oct 1864 (with sporadic usage 1868-1887) 

Type 2 cog on 1861 90c Blue Issue
 

Type 3 cogwheel:

• Different in style to either Type 1 or 2

• 12-12.5 mm outer circle, 7 mm inner circle

• 14 cogs (Type 1 and 2 have 16)

• All cog-tips are blunt/squared

• Integral part of a duplex date stamp device

• Observed usage period: Sep 1863 thru Dec 1867

Type 3 cog on 1862 24c Gray Issue