Good link GLW, that is a good reference.
Co-60 Beta decays to Ni-60 which emits the two gammas at 1.33 and 1.17 MeV to de-excite. This is also the fact with Cs-137 which Beta decays to Ba-137m which then de-excites by gamma emission (662 KeV).
The more knowledge you gain in your craft, the more employable you will become.