Asset replacement by a new one

Hi expert,

Asset are replaced  free of charge by the vendor due to guarantee. In some cases, the depreciation is already started for the old one. Lets say asset bought in 01/ 2012 and deprecation started at this date. In 01/2013, the vendor replaced it by a new one.

Could you tell me which is the best practice to manage the old and the new asset please?

Thanks.

Regards.

A.