Those interested in the history of vexillology have a nice online resource in the form of issues of NAVA News dating back to the 1960s. (NAVA is the North American Vexillological Association, founded 1967.) In the December 1969 issue, a membership questionnaire appears (along with a listing of the names, affiliations, and addresses of all 80 active members).
Of the 10 areas of interest of vexillologists called out, number 8 is sphragistics, sigillography (seals). Phragis is the Classical Greek term for a seal (and is used in Christian theology), as is the Latin sigillum (and is used in Game of Thrones). Your vocabulary has likely just been enlarged!
Is there a North American Sigillology Association? Alas, there is not.
To the extent that vexillologists these days give much attention to seals, it is mostly to deprecate their use on flags (e.g., in the derogatory term SOB: Seal On a Bedsheet). So why does sphragistics/sigillography show up on this inaugural poll of NAVA members?
One possibility is that it arises out of NAVA’s reflexive obsession with its own flags and symbols. NAVA, its officers, its conferences, and many of its invidividual members all have flags. Earlier in 1969 NAVA had just adopted its own seal, after having formed a Flag and Seal Committee the previous year.
In 1968 the organization spent $57.20 to have the seal manufactured — $380 in today’s dollars. It is a nice seal:
Though certainly not as awesome as NAVA’s short-lived first seal, designed by Whitney Smith himself:
Since the Renaissance artists, sculptors, and others have made use of four allegorical female figures, representing the four continents — Europe, America, Asia, and Africa. (See, for example, the end-papers in W.J. Gordon’s Flags of the World.)
Each of these figures is shown with “typical” dress and with an animal peculiar to the continent. America, comprising the whole New World, appears as an Indian maiden with headdress, quiver and bow, and often with a parrot. The armadillo is her mount.
For the seal of the North American Vexillological Association it is proposed to show America and her armadillo to symbolize the geographical extent of the society. Although the arrows of war are not missing, she holds before her a flag to represent the exploration of new territories and a book for the pursuits of statesmen as the sources of new flags in North America.
The flag is that of the Association and of course the book suggests the scholarly interests of its members. Those who wish to do so may read into the armadillo the qualities of the vexillologist — slow but sure progress, a tendency to burrow deeply, and imperviousness to outside pressures.