This letter from Jacob Mears at Cleeve Prior to Bowrey at Wapping was dated 26/15 March 1711/12 despite both sender and recipient being in England at the time. An unusual example of the Julian and Gregorian calendars both being used in the one country. (see On This Day: 24 February 1695 and 20 March 1706)
Mears was about to leave to present proposals to the King of Prussia for a settlement on the east coast of Africa. This scheme was one of the many projects, related to improving trade, Bowrey involved himself in after his return to England from the East Indies. Some of these, including this one, involved trade distasteful today and this scheme was intended to increase the transatlantic slave trade.
We should be grateful that nothing came of this particular scheme.