Last session I had an opportunity to give the mage's guild invite to the player whose birthday a couple weeks ago spurred me to make it. I had an owl deliver it to him (so sue me, it was right at the beginning of the session and I hadn't primed the pump yet). I wrote down his exact words when he first encountered it. They were:
"What does this mean?! . . .
Two circles and a square . . .
ant head . . .
What is this about?! . . .
It's like a yin yang but with more yinyang . . .
and a wagonwheel . . .
travel perhaps . . .
this box with two things sticking out of it . . .
Owl! Come back here and tell me what this means!!"
So, yeah, not much to work with there. I'll keep you posted if there is any more discussion or hypotheses about the invite.