The Blue Tyger (sometimes informally known as “Sparky”) serves as a sort of mascot for the East Kingdom, appearing in its populace badge as well as many of its award insignia.
In a post to the rec.org.sca Usenet newsgroup from September 1993, responding to a comment from Katja Hjalmarsdottir that “Oral tradition has it that the East Kingdom picked an azure tyger in response to the Middle’s dragon…”, Alfgar the Sententious wrote: "... it was I. See Borges BOOK OF IMAGINARY BEINGS… I picked on the Vietnamese version because the Chinese one was a dragon (for obvious reasons)."
Indeed, Jorge Luis Borges’s Book of Imaginary Beings contains an entry for “The Tigers of Annam” (an old name for Vietnam) which begins as follows:
To the Annamites, tigers, or spirits who dwell in tigers, govern the four corners of space. The Red Tiger rules over the South (which is located at the top of maps); summer and fire belong to him. The Black Tiger rules over the North; winter and water belong to him. The Blue Tiger rules over the East; spring and plants belong to him. The White Tiger rules over the West; autumn and metals belong to him. Over these Cardinal Tigers is a fifth tiger, the Yellow Tiger, who stands in the middle governing the others, just as the Emperor stands in the middle of China and China in the middle of the World. (That’s why it is called the Middle Kingdom…
There’s a certain amount of free-association involved in making the connection between the Red Dragon of the SCA’s Middle Kingdom to the Yellow Dragon of China to the Blue Tiger of Vietnam and back to the Blue Tyger of the East, but it does seem to be the authentic backstory behind this bit of our history.
We don’t have an exact date for when the Blue Tyger emerged, but Alfgar became the Principal Herald of the East in early 1972 and the first heraldic registration of the badge is "for the crown" on the August 1973 Laurel Letter, with the association later changed to "for the populace" on the January 2011 letter.
Duchess Diana has reported that she remembers the blue tyger being present when she arrived in the East in early AS VII (summer 1972) to become Queen for Pennsic 1, which would suggest the tyger was already in use a year before its registration.