For completeness, it is worth mentioning that there is a tradition of etiquette that a widow may continue to wear the wedding ring on the third finger of the left hand, but should move it to the third finger of the right hand if she remarries. My guess is that this would also hold true for a widower.

In this way, one can still proclaim love for the lost mate as well as the new one.

I am European (well, British), and know this to be broadly correct in Europe and the US, but can throw no light on TrojanJedi's query.