On p. 153 of The Wars of Reaving, it's stated that the Society used ultraviolet markings to identify themselves when undercover. CSO painter Jal Phoenix stated that he painted an infinity symbol on the back, possibly based on information provided to CSO members at the time. However, it's been some time since then, and Jal himself admitted that it could have just been his own stylistic choice, and I've yet to find a publicly-available canon document that would confirm or deny that as a standard marking.
Is it specifically an infinity symbol on the back?
And, as a follow-on question just to lump it in, are there any other notable symbols or emblems of the Society that have yet to be published?