op AND freckled
Freckled, I dont know if this is what you meant you think should be done, and I havent read the other thread because in some ways what he allowed his family to do isnt really relevant to what is the right thing for you to do.
But anyway, I would have thought that if high value personal effects are normally treated as part of the marital assets, then the simple thing to do is get ring valued, add it to marital assets, you would be entitled to half its value.
Tot up marital debts (could be tricky if some were pre-existing unless youve both agreed to disregard that - HOPEFUL), including outstanding ring costs, and split that.
So perhaps ring will have a value of £800, half of which would be £400 and half the debts are £1200. Therefore if you wish to keep the ring itself (and I think you have every right to do so since it is your property) you would need to offset the rings valuation against your share of the other assets/debts ie you take £1200 debt, add £400 since you want the ring, and keep £1600 debt plus ring.
Alternatively, you offset ring value against £400 of current value of stuff in the marital home that stbxh wants eg sofa/hifi etc
This is completely fair and if you are willing to do this then it is absolutely your choice whether you keep the ring of not.