In the first book of the Amber series, when Random and Corwin travel to Amber, Random "adds" Corwin's sword when travelling through Shadow. The same thing happens in the second book, Guns of Avalon, when Corwin finds his sword in a tree trunk:
It mattered not if it had been somewhere in Amber. It was here now, for the wood that I walked was in Shadow.
Later in the series, however, we learn that it is impossible to find and transfer particular thing through Shadow. So, was Corwin's sword a copy in these cases, or did he have the power after all?