The caption above it appears to read "Gregory XIII Pon(tifex) Opt(timus) Max(imus) in the Year VIII" In the center is a stylized owl with a dragon in its heart. There is a lot of symbolism here, and I will not get into all of it. It appears to be associated with one pope.
I do not know that this resolves the question of the guardian, but it is interesting. (Or I may have missed something that resolved it in the 600 posts I skipped over this evening...)