You might get more responses in the California section.
I know that CA law says that a gun "carried openly in a belt holster" is not concealed. CA law doesn't necessarilyrestrict that to being the only thing that is not considered concealed, but if its carried openly in a belt holster it shouldn't be considered concealed.
Isn't theBlackhawk Serpausually usedOWB?
There are a lot of other restrictions in CA too that you must be aware of, if you aren't already.
For example, when knowingly within 1000 feet of a school your gun must be unloaded and in a locked case.
Also, in areas where discharge of firearms is prohibited (such as practically any city and many other places) there can be no rounds anywhere in the gun (no rounds can be chambered and no loaded magazine can be in the gun). A loaded magazine can be carried openly (on a belt holster for instance) but a loaded magazine cannot be concealed either as a concealed loaded magazine is illegal. However, a concealed speed loader for a revolveris not illegal.