March 1 (1853) to New York - CDS with integral "PAID 6" and manuscript "pr Str Oregon" endorsement.  CDS indicates the pre-paid transcontinental 6 cent single rate.

This was the first CDS to incorporate an integral PAID marking.  This is a unique style CDS which is easily identified and was used during a portion of the pre-paid 6 cent transcontinental rate period of July 1, 1851 - March 31, 1855.  This  version ultimately replaced the 35 mm sans-serif CDS with the large numeral 6 at bottom.

Some of the unique identifying characteristics of this CDS are; 
33 mm diameter
Serif font
"CAL" at right side and not bottom
"PAID 6" at bottom (unique style to this CDS)
Day/Month only, no year

An additional example of this CDS is shown below.

December 1 (1852) to Baltimore, Maryland.  A similar example to the cover shown above, CDS in blue ink.  This ink color was used by the SFPO from August 1852 to January 1853, so covers showing this CDS color can be dated even with no year markings present.

Earliest/Latest Found Dates (Bookends) For This CDS
Ref # Rate Date Destination Image
SF IntPaid6-1  Earliest 6 November 1, 1851 New Jersey
SF IntPaid6-2
6 July 16, 1853 Michigan