There are a bunch of early nineteenth century letters featuring family arms in the upper left hand corner. The style is ubiquitous amongst correspondence to clockmaker/conchologist Benjamin Lewis Vulliamy, so I’m thinking the paper crests were added on that end at some point.
In a couple cases (e.g. the Shaftesbury bull, 23 October 1815) the image was pressed into a fat glob of red wax. In others (e.g. Lord Yarborough, 25 June 1815) the arms are cut from a different sheet of paper and glued in place. There are also cases where a brief bio is pasted beside the arms (e.g. Bishop of Lincoln, 25 February 1818). And the Marquis of Queensberry (15 April 1820) has the arms glued beneath his signature and a glob of black wax in the upper left-hand corner. They’re quite different: the crest (a crown over a winged heart) in wax, the pegasi supporters and motto (“Forward”) glued on. I spent some time googling family crests, amused by the density of description in digitized nineteenth century heraldry books, and wishing for links to illustrations (rather than references to plates, if that). I should bone up on my heraldry terminology.