First time I see a Cas. coin with a "Certificate of Existence".
Is this certificate from Casascius?
Doubt it. If Im well informed then the only certificates that Mike provided were digitally signed ones.
My gut tells me that its one of these:
https://bitcointalk.org/index.php?topic=221343.0.
I remember wanting to buy a couple but unfortunately they ceased selling them following a fire in their offices.