Cobalt-60 is more dangerous than Caesium-137 in every way except for chemical reactivity. Any significant amount is extremely dangerous. Don't be fooled: what you held in your hand was a vanishingly small source.

This little pdf has some metrics for comparison:

orise.orau.gov/files/reacts/radiological-terms-quick-reference.pdf‎

Edit: I haven't the brains to make the link above active, but if you search for the link on google it will take you there.