Tiffany & Co. Extra 925 Hallmark

On the back of this return to tiffany heart (attached to a pearl bracelet) there’s a 2nd 925 hallmark. Does anyone know what this means or if this is normal? This piece was authenticated already so I know its real, I just have no idea what this marking is.

Thank you!

The 925 means it’s 92.5% pure silver (the sterling silver standard).