First, the trust may have a general assignment clause that effectively titles all of the decedent's tangible personal property to the trust. If so, then all of the artwork, coins, etc. is trust property -- and, that resolves your problem.
If there is no general assignment clause, then the unassigned tangible personal property is part of the decedent's probate estate and it is subject to disposition under your father's Will, or if there is no Will, then under the intestacy code.
Usually, when a revocable trust is made, it is accompanied by a pourover Will, that accounts for all of the property not included in the trust and puts it into the trust. If there is a pourover Will, then that document controls the dispostion of any property that is not in the trust already (assuming no general trust assignment clause).
And, here is where it gets tricky.
California is a community property state, and under its laws, a surviving spouse can force a one-half share of the entire community property estate, despite any acts of the decedent spouse, such as placing that community property into a trust. So, if any of the property in your father's trust is arguably community property, then his spouse can force that one half share.
And, since all earnings during marriage are community property, anything collected by your father during the time he was married to the surviving spouse is very likely one half hers, regardless of any trust or Will instrument to the contrary -- because the earnings used to acquire the property was one half the surviving spouse's.
This all gets VERY complicated, and could lead to some very expensive litigation and accounting expenses, unless you and the surviving spouse can come to some sort of agreement as to the disposition of the estate.
I could go on with this subject for about 100 pages, but suffice it to say, that if there is a lot of valuable property at stake, then you need to sit down with an estate lawyer and work through an accounting of everything to see what may reasnably be community or separate property. Because until you do that, all of the other issues that you are raising are subordinate.
Hope this helps.
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